The gear ratios are quite different. The T-56 is basically a wide-ratio four-speed with two overdrives. Fourth gear is 1:1. With a Richmond, you have a close-ratio 5-speed with an overdrive added. Fifth gear is 1:1. The Richmond is probably an easier swap, with the stock clutch linkage, bellhousing, etc., being used, while the T-56 requires much more modification. The T-56 can be bought from a wreck & made to fit, or you can get kits from aftermarket sources. The Richmond is an aftermaket-only item.