1974 Firebird
 

A coworker of mine has a 1974 hes looking to replace the wheels on. He wants to run the widest wheels possible without modding the car itself and the flushest as possible in 17 inch staggered fitment. It was originally a straight 6 car. How do we go about figuring out the offset? Hes sticking with the factory rear axle with the factory drums for now. Any help is appreciated.

A quick search will turn up some good wheel fitments but as a rule of thumb with 18" wheels you can easily run a 255/40/18 up front with 4.5"bs and a 295/35/18 out back with 5.5"bs (that's what SW was running on his stock/lowered red 73 T/A btw). Many have done it and it looks great! Now for 17s and to be a bit more conservative maybe go with 245/45/17s and 285/40/17s out back. HTH

So im gonna assume he could run a 17x8 up front and a 17x9.5 out back? With that backspacing? Forgive the silly questions but im still not very fluent in offset and rim widths.

I have a 74 too and I am going with a similar fitment as SW's that Ty mentioned. I bought some used tires to get it rolling on and they are 275's going on a 9.5 wheel. Eventually, I am hoping to go up to a 295 although that is pushing the limits of a 9.5 wheel. Mine are 18's.
One thing to consider, I am not sure if the 70-73's have the seatbelt hump that the 74's do, and that may need some massaging to fit the widest tire possible.