And I need to know if there is anything else I need to put them on my base Firebird.

I am looking at a site that sells rear spacers for 16 in wheels. And they also have lower control arm bumpers for cars with 16 in wheels.

Are these necessary to put these wheels on my car, or can I just bolt them on and go?

EDIT: I forgot to tell you about my car. VIN calls it a Formula, but it has to be a base model 1992 Firebird. It has the 5.0 TBI engine. It had the GTA kit and 15" GTA wheels, and I just had to get those wire looking wheels off. I want to put the Formula wheels on it and a friend of mine just gave me a set as an early Christmas present. I need to know if they can be put on this weekend and work, or if I need more for them first. I will post tomorrow with the size of the tires. But I know the front wheels have the same size tire as what I have on. The rear wheels are different, 245's instead of 255's, I think. That may look odd.

Bolt them on and go. Make sure you put the front wheels on the front and the rears on the rear. Also, there were NO 15" GTA wheels. They came in 16's ONLY

On some of the 16" Formula-T/A-GTA rims the front/back is stamped into the back of the rim web so make sure to look close.

And yes, you probably have a base model firebird with the W68 aero package (ground effects)...

W62

W68 is the package that came on base model 91-92 firebirds (which still had the stock spoiler)... W62 might be part of the trans am package with the ground effects and the aero wing?

If you have drums in the rear (probebly) use the spacers (but you can get away without) With rear disks do not use spacers.