Based on the 3 options, no doubt I'd go t56. It is the most work also though as mentioned, takes some cutting. I wouldn't mind having one of Passons 5 speeds for my belvedere, but I lack the patience to wait for one.

68 Road Runner, 69 Belvedere, 71 Challenger Vert
340 barracuda, 01 Ram CTD, 95 Ram, 04 Ram, 85 Daytona turbo Z
66 GTO, 06 Magnum RT AWD. 07 Ram CTD, 07 Ram