The track width and the wheel base are the same. Not sure if the offset is the same. The 90 has 17 in and the 85 has 16 in wheels. If you check aftermarket wheel sites , many give you offset specifications.
I dont believe it is the offset, but the brakes. 84-87 had a smaller rotor 12" I believe, 88 and up used 13". That is why you have to put the wheel adapter on 84-87 vettes if you want to upgrade your brakes. So 85 wheels will not fit on a 90.
'13 427 60th vert - '21 Silver Flare Coupe - CTS V Wagon(4-door Vette)
If the 90 has the big brakes (J55) - no.
Besides, there was a change in suspension geometry in 88 when the 17" wheels came out and that changed the offset of the wheels also. The early C4 has a 32 or 38mm offset while the late C4's have a 56mm offset.
Even if the 90 has the 'standard' small brakes, the early C4 wheel will stick out of the fenders.
Additionally, finding correct 16" tires is getting more difficult every day.