pop the distributor cap, remove rotor arm, remove metal disc shroud and look at the points, the shaft that is sticking out from the centre where the rotor was also has a cam on it where it opens and closes the points - the gap to set here is that. align the engine so that the cam flat is facing the points heel - adjust the points so that only a 0.45mm feeler gauge leaf neatly fits in there.
you can make your own tacho if your multimeter can read Hz.
your ignition coil fires 3 times for each engine rotation, so
if we read 45 hz - and multiply that by 60 we get 45x60 = 2700 pulses - then if we divide this by 3 we get 900 which is rpm.
You need to read it off the coil negative side.
the ignition timing can only be set with a strobe gun.