Since it looks like you'll be in the Cummins area for load, check out Goerend Transmission and SunCoast Performance. They specialize in the build and pieces for the 47 and 48 trans so that they'll live under high torque and loads. Also there may be someone in your area that caters to the Cummins trucks with auto trannies, ask around. You could also get in touch with A&A out of Indiana.