280ZX models have been fitted with:
Denovo Denlocs - metric wheel, no tyres now available to fit - forget they ever existed.
Iron Cross style 5.5" x 14"
Later 6-spoke design 6" x 14"
Standard recommended tyre sizes are 195-70 14 or 205-70 14
As a fatter upgrade, a 225-60 14 would have more or less the same rolling circumferance as the 195-70, but would be a bit "fat" on a 5.5" rim.
All 4 stud Z and ZX models have the same 4.5" or 114.5mm PCD which is shared by very few other cars - from memory, Triumph Stag, Reliant Scimitar GTE, Mustang II, early Toyota Supra..........hence lack of modern wheels suitable!