The dual-range Hydramatic in that truck has a variety of bellhousings that bolt to the main transmission. You'll need the bellhousing that matches whatever engine you choose to make it fit. Hydramatics were also used in some non-GM cars such as Lincoln Continental, Nash, and several others. Of course, the mid-50's Pontiac, Cadillac, Oldsmobile, GMC, and Chevy trucks all used the Dual Range. I think the 389 Pontiac and the later model Olds and Caddy engines had a different bolt pattern for the Turbo 350 and 400 transmissions.
Jerry
