I don't think you can do a top swap because of the tuning issue. I could be wrong, but I know the last year grand prix can't be top swapped, and possibly the 07 model as well. we have a member that is in progress of doing an LS4 swap as we speak, and has paired it to a 4T80 transmission, because the 4T65E will not be reliable at the power levels an aggressive LS4 turbo build will make. Look up Furches Performance, he is the shop owner doing the swap.