Welcome to Hybrid Z. This is the best place that you could have come for info. I have an '84, with a 355 and a 350TH. Unless the tranny is weak, it should take all you are gonna give it. If you are going to change you might want to consider a 200R4 The only reason is because the 350 is a direct drive and Z31's are geared a little low. Any questions you have just get ahold of Alf or me.
Good looking car. I think the guy who had it before was on here, but I can't remember what his user name was.
Joe