What rear end do I need?

The 8 1/4 is a great rear for the price.
8 3/4 is a complete waste of money when you can build a D60 for less.
Stroker motor never messed with the 8 1/4 but I built a 8 3/4 before I broke it and broke that within 20 passes and built the D60 and done. The 8 1/4 was great and all with 355 gears and that I was still at about $300 and sold it for that.