Top change and bottom change driveshaft length

Quick query here. I am aware that the top change and bottom change gearboxes use slightly different length driveshafts. I am in the process of rebuilding some driveshafts for my 70SX top change conversion and have two sets. The shafts for one side most definitely differ, there's about 3 - 5mm difference in the shaft length. The question is, which is the correct shaft for the top change gearbox - the shorter or longer version?

Back in the day with my original mk1 UT I wrongly fitted the passenger side driveshaft from a top change car when I did an engine change and a few months later I heard a loud bang while driving...upon stopping I found that the bolts holding the inboard CV joint to the diff output shaft/cup had vibrated loose, releasing the whole thing to smash a hole in the side of the gearbox...I deduced from this that on the passenger side at least the top change box driveshaft is longer, and by forcing it into my bottom change car it was compressed/bound up causing the vibrations that undid the bolts.

So, to answer your question, I *think* the top change driveshaft is the longer one (on the passenger side).

Thanks for that information Jas. I believe that the top changer has the longer shafts too though I'm not entirely sure. I have another issue now in that I can't get the damn outer CV joint back on. Why did Fiat use that stupid snap ring/ jump ring design to locate the CV joint in the turbo model instead of the simple circlip they used on all other models? Grrrrr....