Well, you could install a 67 b body rear end in your 70, that gives you an inch, then a 1 inch spring location on top of that. On my car I run 275x60x15's on the back with either 7 or 8 inch rims, I have used them both. 7 inch on there now. I am doing a b body dana with a relocation kit. 10 rims will let me run a bigger tire for some better 60' times and better ET's.