Coupe and sedan front struts are the same, so fitting the lower coupe 7 wind springs and the matching shorter bumpstop is the factory solution... definitely doesn't bottom out the strut rod internally when the bumpstop hits bottom.
If you want early pre 1979 x19 rears I have a huge bunch of genuine Way assuto rears available... like about 60 struts NOS.

mg:
Yeah a shock dyno of the different items would be nice ... you would need a bunch of NOS struts to test though to compare, on the same shock dyno, same day, same operator... and realistically when is that ever going to happen.
I think you will find what I'm saying is correct, generally FWD cars have stiffer rebound/extension damping to counteract the front end lift... which is why on a 128 with tired struts the first symptom is the front end lifting madly... not the struts weeping or the car bouncing.
Nice CAD btw... though the measurements I have put the lower mount holes in the same positions (with OEM way assuto struts - so the KYB's might be a little different)
Albert,
the strut shaft dimensions for ALL x19 fronts is like the early rear strut, the late rear struts different dimensions will preclude the use of the early front or rear bump stop/bush assembly... so you cant do it unless you have the strut shaft machined down....late rear bump stop assemblies (which will fit the late strut shaft dimensions) won't allow any pivoting motion, so are unsuitable for the steering end.
Machining the late x19 rear strut shafts is certainly possible and doable. You could modify your existing 128 bump stop assemblies by shortening them, that's quite easy as well, drill out three spot welds that hold the collar which the rubber bump fits into, then shorten the tube, and re attach the collar. Use the 128 front top mounts and leave the body alone, 128 mounts are a lot cheaper and easier to find than x19 ones.
SteveC