I had the same thoughts as Uncle Bob, that a TKO-500 would be a good fit for your mildly built 283, or that a T5 would likely work OK, too, and is substantially smaller which might help your fitment issues. I ran across a pretty good history of the T5's which explains what they were in, and even some mix & match that can be done to move the shifter around, etc. Be aware that some of the OEM units, like those in a lot of Camaros and Mustangs, may have been used and strongly abused, making them virtual grenades waiting to explode. Be prepared to go through anything you buy used without personal knowledge of it's history. Here's the link to some history - History of the Borg Warner T-5 Transmission; Mustang, Camaro Firebird, S-10