Sh Ltd have this spring compressor, they also have a very basic optical alignment machine but they have one critical piece - the five finger unit that goes into the wheels - if you notice all mercedes wheels have 5 little holes near the lug bolts, they are placed for the alignment jig so it can directly rest on the hub and they also have the spreader bar which is nothing but a spring loaded bar placed between the leading edge of the front wheels. And they know the steps to align the car - the trick only lies in the steps.
if your alignment shop does not have that mount jig (which they wont), then get them to mount the regular large clamp to the wheels - the car can be aligned by it too.
centre the steering perfectly - loosen the tie rod adjusters fully and dial the toe to zero - now set the caster angle, and whilst testing and returning it back to the centre position make sure the toe is zero again - then proceed to adjust the camber - dial toe to zero again and then do a final test on both camber and caster to ensure they are perfect and toe is zero.
Now adjust the toe in - but first arrest the steering wheel dead on center - the spreader bar can be duplicated with a jack and a piece of wood slightly tightened - its only job is to simulate spread out as the car will roll down the road in real life. There is a slight difference, dial an extra few minutes if you dont have the spreader.
I find it best to repack and readjust the wheel bearings with fresh grease before alignment is done on these old MB.
p.s. if you find one wheel is sticking out of the fender more then check the alignment of the body panel rather than assuming the frame is bent.