Best thing to do is go try out aftermarket seats and get them to fit

 

Reasonable advice most of the time, but not now. It's a long way from home to any dealer who would actually have demo seats. OTOH, used G37S seats are readily available, and they fit my shape nicely. All that remains to convince me to get a Z is to find out if the G37S seat can be made to work in a z33. Lack of affirmative responses does cast doubt on the possibility.
Z91Doc

 

Most people with these cars wouldn't go through the trouble of swapping the seats to something more comfortable. They would swap to something more sporty, unfortunately that basically means it will be difficult to get any answers.