I have an 88 base firebird. want to replace the 15" camaro RS previous owner put on and was courios what sizes i could use

15,16,17,18,19,and 20.in other words any wheel that will clear your brakes and the body.

You can use whatever wheels you want as long as you buy tires accordingly. On a 16" wheel you would use a 245/55-16 tire but on a 20" wheel you would need to use a 245/35-20 tire

Also keep in mind, as you start getting into the sizes above 16", you may have to run some type of spacer depending on the offset and backspacing available in the particular wheel you want to run.

thanks for the input guys