47-55.1 Help Determining wheel size on a C4 IFS & IRS 55.1GMC

[JDarby]

Hello All I am at the point in my project that I need to hone in on wheel size
and tire size for my project.

Up to this point my truck has been sitting on 15" tires and wheels
borrowed from a 62 Impala minus my calipers and rotors.

To complicated matters I have bought a C5-C6 caliper adapter kit to increase my front braking power.

I do know that with the C5-C6 caliper my wheel size will at the minimum be 17"
which I'm good with.

So here is what I am asking, what is the most straight forward way in determining what wheel will fit in my fender wells?

My rear will be stock C4 set up, and I do not have any corvette rims to
test with.