Hey mate,
The standard FD seats are quite good, I like them and I think they would fit well, since both the FD3S and S30 Z are very narrow in terms of seating and so you shouldn't have door card rubbing issues etc..They are a good trade off between bucket seat and every day suitable seat. The only downside is that they are quite heavy and would need a re-trim to suit the S30Z interior look etc...
A really great seat and what I have in my FD is the Recaro's RZs with Tilting Rail Function. The benefit of these is you get a fixed bucket seat that can be adjusted titled forward / back and slide forward and back etc.. It is now hard to get into and out of the FD but it is a good compromise and best of both worlds. The only problem is these seats are very expensive - even second hand in shagged condition.
They come in black and red.
To my knowledge I don't know of any other bucket seat that has a tilting function like this? I've often thought about taking them out of the FD and putting them in the S30Z and putting the normal FD seats back in the RX-7, since they would fit in the tiny S30 cabin. If they were not so damn expensive I'd buy another set.
Another great feature is the seat belt strap so you don't have to fish for the belt behind you, although if you go a harness this is a moot point.
A guy has replicated them here:
http://www.angrypandafactory.com.au/
But he is having issues getting the rails sorted and I've been waiting ages for him to replicate the rails so I can buy 1.
A similar seat to the Recaro RZ (Spirit R Type A) seat is the Recaro Pole position seat, (Mossy) - Mark had these in his orange S30Z and they looked good, but he swapped them for some Datsun competition bucket seats.
You could re-trim them to have the Datsun style vents in them like this 432 appears to have had done.
The Recaro seat shape etc.. would suit the S30Z in my opinion.
I've been looking at the Datsun bucket seats since I really like the look of them, but you need the headrest for sure. The only downside is comfort wise they might not be great.
A similar seat to those is the 432-R buckets like seen here:
Think they are the same as the old Rally cars had.
Where would you get them? No idea. I think Alan T (HS30-H) had some copies made a few years ago if I recall what he said correctly?
I have a set of reclinable Recaro's in the 72 240z, they are comfortable but they look too big and chunky for the S30z and I want to change them in the future.
I like the period look as you can probably tell, even if it means a trade off in comfort to some extent.