i am looking into getting some prostars and was wondering what size rim is best and what size tire should i run? what backspace will fit the ls1? 4.5"? or 5.5"?

 

In the front, the only choice is the 15x3.5" 1.75" BS. Whether that fits without a spacer on the LS1 brakes I don't know. On the LT1 it takes a 5/16" spacer to clear the springs that hold the pads to the caliper, and the big horizontal bar on the steering knuckle that support the caliper.

In the back, either 15x8 5.5" backspace, or 15x10 7.5" BS. Again, on the LT1 rear brakes, the corners of the fins on the caliper need to be ground down. Not sure if this is an issue on the LS1 cars. An 8" wide wheel is OK for most 10.5 wide tires, while a 10" wide wheel will handle any width slick that you can physically fit on a 4th Gen without tubbing.

You will need longer studs front and back to meet NHRA tech.

 

does anyone have a part # for a weld prostar 15x8