wheels are all the same on all 1500s & 1800s
doors from '66-'69 are interchangeable, same for 70' on wards (read '73)
bonnets from 1800's fit 1500's but don't match up perfectly with the 1500 cow panel
two different types of 1800 hubcaps, one style has a ridge around the outside and the other one doesn't
1500 wagons have an extra rear leaf 'load' spring (about 2x as thick as the rest)
RX5 wheels bolt straight on, if there was something that had to be done it was only machining out the bore a few mm's
RX5 diffs also fit into 1500/1800s nicely obviously with mounts changed
parts that don't swap between 1500s and 1800s (door handles, door jams, tail-lights - despite looking mostly the same, doors, etc)
earlier cars (66-68) have different shape side repeaters for the indicators than later cars (69-73)
VB/VC/MA engines just swap over
really really early 1500s had the same tiny front guard indicator lights that on some R100's and 1200's. there's two types of side indicator lights, too. the early kind are quite tapered front and rear and are more "full" and the later type are more rectangular and "flatter". A7 indicators were identical with ...L10B Cosmo, RX2, 1200/1300 etc.
the early 1800's had the same hubcaps as 1500s
Knox Auto Carpets (Victoria/Aus) make new carpet for 1500/1800 in a variety of colours
Aurora Springs makes the custom lowering springs
A6 1500 SS grille is the same as a normal 1500/1800, minus a couple of bars (probs to help cool the hypo SS model) and an SS badge
A6 1500 SS factory issued wood grain steering wheel is very similar to R100, but its a slightly larger diameter, different colour wood and different horn button
A6 1500 SS trim is R100 spec. The basket weave in the seats is identical and the roof lining is the same perforated material
A6 1500 SS factory AM radio and electric antenna is R100 spec.
A6 1500 SS has Neo Nazi looking SS badges on the C pillars. another SS item is the SS badge to the left of the rear plate
original wheel size: 6.45-14 (modern day equivalents: 155R14, 165R14, 185/70R14)
original stud pattern: 14" - 4x120mm
1500 Standard: safety padded dash, seat belt anchors, an advanced fresh air system, crash proof door locks and a re-enforced passenger compartment, windscreen washers, reversing lights
1500 DeLuxe: a radio with power aerial, foldaway armrests and a dashboard fascia mounted electric clock
1800 achieved its extra capacity by increasing 1500s stroke from 78mm to 94mm (104bhp)
1800s: torque: 109 ft/lb. at 3000 rpm using a 3.7:1 final drive ratio
1800 gearbox ratios were the same as the 1500, but the final drive substantially increased the range of the intermediate gears. the gear change was floor mounted
1500/1800: one lever on the steering column controlled dipswitch, headlight flasher, windscreen wipers and washers
1800 came with reclining seats (with headrests), a push-button radio with power-operated aerial, electric clock, generous courtesy lights, a full range of instruments, demister, tinted windscreen and quality ventilation system
1800: steering was by recirculating ball-type, with 4 turns lock-to-lock, the turning circle was 32 feet
A6 and A7 body types (apart from the already discussed); SS models: A6 rear beaver SS badge is on the passenger side of the car. A7 badge is definitely on the right hand side. A6 rear bumper brackets slide in between rear chassis rails, A7 rear bumper brackets bolt to rear face of the chassis rails which in turn make the rear bumpers different due to the mounting bracket holes
1500 has 50ltrs. tank
Rx5 & 121 disk brakes can "work" on 1500s and keep the pcd (4x120mm)
1500/1800: A7 & A6 differentials are totally different
the A6 and A7 differences: A6 has the cast headlight surrounds, sort of oval shape front side indicators, dash vents under dash not in dash, interior door handles are the pull up type instead of pull towards type. A7 has tin headlight surrounds, interior trims are different, dash vents in the dash, side indicators are rectangular (not as nice looking). A7 started in late 69. Another difference between A6 and A7 cars is the steering wheel. one more thing is the windscreen rubber & finishing; early has aluminum, late has stainless steel. two completely different rubbers too
SUAV is the wagon's chassis prefix in both cases, A6 and A7
UB series engines: oil filter is the cartridge type that sits in the tin cover not a spin on type
if anyone gets stuck with the UB motor cartridge oil filter and cant find replacements, the filter adapter off the 626 MA motor bolts straight on and a spin on filter can be used
to remove an aerial switch: remove center glovebox, normal glovebox, radio out - all to get to the 2 bolts holding it to the back of the dash pad
A6 has a single push brake master with only 2 outlets (one goes to front right, the other goes across the firewall and splits to do front left and the rears) and it shares the same fluid reservoir as the clutch (joined). the A7 has a 3 outlet brake master (tandem push) (similar to later mazdas) and uses separate reservoirs for clutch and brake. they may be interchangeable, as they look to share the same mounting style/hole centres (don't quote me on this last part on interchangeability)
aluminum light surrounds of the front blinkers/indicators which go under the front bumper are a straight swap between A6 and A7
rear leaf springs on 1500s are 60mm wide
1800 engine bolts straight into a 1500, but you need a late or early 1800 model bonnet (the one with a scoop or scoop and side moulds)
A7 windscreen and back window, both are interchangeable with A6
1500: complete clutch slave assembly (including pin and springs etc) #0223-41-920 or just clutch slave body by itself #0223-41-311
re-synchronizing the wipers: once they go out of wack, the cable between the wipers stretches and they cant be fixed without replacing the cable
only very early models had the clock on the dash the top mounted clock was available as an option. if your had it fitted from factory, you'll have a recess and a few holes from where it was mounted. dash clock hole is approx. 20mm in the very centre on the dash pad. in 1968, before the big changes came (i.g. the so-called A6-A7 split), the clock is moved next to the meters. in some cases instead of the common to A7 cars clock with the silver coloured metal "ring" there was a black one as well. a deluxe car had a clock as standard (non-deluxe did not have a clock or radio), as mentioned earlier, depending on what model (A6 or A7) meant where the clock was placed A6 on dash top and A7 in the dash
A6 and A7 have different window regulators in the doors
the chassis number is stamped on the firewall below the front windscreen inside the bonnet, towards the right. also have a VIN plate affixed to front firewall right over where the chassis number is stamped
wipers assemblies have a A6/A7 split
an 1800 estate version (model SVAV - station wagon) was added in 1970
ps: this is the fact sheet on 1500s/1800s i have been able to put up after some research. this however, is in no way 'complete'. if you know anything which is not listed, please feel free to add.
some more info, as shared by a hobby friend from cyprus on the subject of A6/A7 split
also i have realized that different models came with different bonnet designs. for instance this is the bonnet on my 1969 A7 1500 base sedan
however, this discussion on the bonnets is still under debate among the veterans and i would update the information on bonnets accordingly as soon as we are agreed on what actually was the basis of this difference (whether models A6/A7 or the variants 1500/1500SS/1800 etc.)