Has anyone done a 68-72 chevelle rear swap into a g-body. I know the chevelle rear is about 4" longer axle to axle, the LCA are mounted the same but the uppers are not. I think umi performance makes uppers, want to run a 8" wheel, what backspace would i need, its a 8.5 rebuilt with a posi and 3:73's for $400. Thanks