I don't want to re-invent the wheel

I ran a 245/50-15 on an 8"Rally, on the front of my lowered Barracuda. It was very tricky, with a lot of finessing.
The current wheel is a 7" with a 235/60-14, which is a bolt-on and go deal. I think it is a 3.75bs, but it's been a lotta years since I looked.
I'm pretty sure you could run a 235/50-15 no problem, also on a 3.75bs.
Others will chime in

As for the rear, and with the spring relocation. 15x10s will physically fit in there, but the bs is critical. I run the standard 4.5bs but the rear has been narrowed about 1.5 per side. The math thus says you would need a 6"bs to tuck the wheels in to match my install.
At 5.5 you will have lots of clearance to the inside, but may have to get creative on the outside. In fact, I would test fit them before I went thru the trouble of relocating the springs
This is not that big a deal, cuz you can always narrow the rear atta later date. At least you can drive it with SS springs.

If you have the KH 4-piston calipers, you will have to be careful with wheel selection as not all will clear the calipers, in stock form.