the stock pressure plate is about all there is unless you expect to spend some money. other than nismo, there is one made by Center Force that is stronger than the stock one.
the disk you use will depend on which trans you use. some of the early 5 spds. were nothing more than an L series trans with a different housing, they have a larger diameter input shaft. here (US) they came in the B210GX and were used through 1978 the later B310 5 spds. use the same disk as the 4 spd.

the VG30DE(tt) came in more than just the Z car. believe it or not, it will fit, I have seen them in 510's and 1200's.
it looks bigger than it really is because the Z32 (300ZX) enging compartment is so small.

you said that the axles came out of the same diff., BUT did or did you not change the axle housing? if you did, measure the didtance flange to flange and make sure that they are the same.
like I said berore, it sounds like you axles are hitting the diff center shaft, the only thing that causes that is the axles being too long for the housing.

why not just use a VG30DETT out of a 90+ 300ZX, 300 hp and it keeps it ALL Nissan?
btw, the n/a version is 222 hp.

another thing to consider, is it possably the clutch shuddering and your thinking that it is farther back in the car?
a broken main rear leaf spring could cause this, but you should be able to see it. also check for worn or missing spring bushings.

it sounds like the axles are too lpng and are pushed in so far that they are hitting the spider gear shaft. either that or there is a lot of dirt or rust on the area where the bearing sets. but where you stated that it binds up, I would say check your axle length.
if the axle won't slide back out, get a length of heavy chain, attach one end of it to the axle on a lug stud with a lug nut and whip the chain to work it loose. that way you can get it out without danaging the axle or housing.

look at it and see if it is just a flat spade terminal held on by one of the screws that retain the vacuum advance diaphram.
if so, and I think that's all it is, it is a ground hookup for a noise supressor condenser.
you don't need to hook it up to anything.

SU's are basicly the same through out all the years try this site; www.jetlink.net/~okayfine/sutech.html
there is plenty of info there

there are several things that I would like to write up as tech articles, but it will have to wait at least til the Branco brothers return.
items like;
rear disk conversion,
cheap flat top pistons (good for about
15 extra HP. in a stock A12),
which 5 speed is best and why,
and the like.

I also have a set of micro fiche for USA models that I am working on getting onto CD, once it's done any one who want's to buy one can look up their own parts.
depending on how many want one will determine the actual cost.

I figured that would get someones attention.
send me a note privately with your email address, I'll explain