These are a straight fit to convert the rear of a 280ZX to 5x114.3 all you need are some axles and brakes to match, new Z31 wheel bearings and new spacers to go in between them which are available from Nissan for around $35.00 each.
Looks like it will be pretty much the same for an R30 using S14 5 stud rear rotors, I think they'd fit 1600s and 180Bs.