Iv'e used 4 7/8 backspaced (8.5"Centelines though) and fit absolutley like a glove with the leaf springs in stock location. Im quite sure thats the limit before the tires contact the springs and you don't want to run wheel spaces thats a big no no. I think a 8.5" rim is fine for what you need. Heres a pic of the c/ls with 3300lb super stock springs. this car has 60' a 1.46 with a 7" rim on a 10.5 tire.