Does anybody know what issue of HRM the original article on the X Shift appeared? As I remember the original was developed by a trans rebuilder in LA who used Chevy 37-54 truck trans cases and fitted 55-up gears. I think he got Offenhauser to make aluminum cases after he had trouble finding the Chevy cases.
The article is in Hot Rod Annual #2. The shop was Trans Specialties, it was owned by Lou Sales in the L.A. area and yes Offy cast those cases for him. It was fairly short lived because the Warner T-10 4 speed came on the market about then and no one wanted modified 3 speeds after that. I have built a couple of those boxes and they work quite well but they are no stronger than any other old Chevrolet 3 speed. I have the article and could make you a copy if you would like one.