Well ill be rebuilding my rear end soon if everything goes well and im considering a gear swap. I currently have 3.73s in, but im thinking the extra mpg cushion that 3.55s will offer might make it worth swapping. Right now playing with all sorts of numbers, 3.73s look like they are the gear I should have. If all goes well with my 5.4 swap, ill make somewhere between 400-500hp NA and I have every intention on spraying on top of that. With 3.73s, ill be good to ~140, 3.55s will take me to 147. With spray closing in on 140mph is looking like its possible so im wondering if I should swap in 3.55s just so I don't have to worry about running out of gear. Any opinions are welcome.