Used gears are very hard to find. 5.12 is the best all around gear but 4.88 is next in line. They never made any gears except a 3.9, 4.1, and 3.39 that bolt into these cars. All the other ratios must be custom made for them. I have the 4.88 and 5.12 in stock ready to bolt in or can do the modification to the various gear sets that fit. Just giving you some options, not pushing my products.