Will these fit?

[LS1_ws6]

I found these wheels on craigslist but dont know if they fit my 99 trans am.

http://denver.craigslist.org/pts/1347353200.html

[T/A Turbo 1989]

Those wheels have a Neutral offset. In other words 4" on each side of the mounting part of the wheel.
Your T/A runs a positive offset wheel.
So they will likely stick out of the wheelwells a few inches.
The bolt pattern is right so they will fit on the car's lug studs but the offset won't be right.
It's a long drive from Brush down to Denver but you could take the drive and bring your floor jack and try them if they will let you, put one on front and back and see if you like the look.
The tires on those wheels are narrower than what your car uses but the diameter of the 245/45 will work and be very close to the stock look Overall diameter wise

[LS1_ws6]

thanks for the information man.