Thanks thoroco for your reply, I'm trying to decide which will be the cheapest route to take. I have the 12 bolt that was original but not sure of gear ratio and it is just the standard diff with one wheel the pulls. I do have a 9inch that has 350 gearing and is limited slip and believe the tracking is the same width. I also have a 1990 chev pickup that I intend to use motor and transmission but I'm not sure if the diff would be wider than the original out of the 72 c10