A much simpler swap would be to install the SM 319 OD transmission and you'll have five forward speeds available, not four, and have overdrive to boot. As long as the vehicle speed is above 30 MPH or so, depending on the rear end ratio, OD can be engaged with the transmission in 2nd. gear. If you want to use 3rd. direct after that, just make the manual shift and use the kickdown switch to get 3rd. direct. I learned that trick on a 53 Nash Ambassador in the late 1950's. I was even able to use OD in 1st. gear, but getting that old Nash engine wound up enough to trip the governor in the B-W overdrive probably wasn't the best idea I ever had.
Jerry
