3 different years, same transmission, which one should I use?

gotta agree with sniper. Use the 904 trans. Maybe all 3 are 904s. The 76 trans would be best choice as 66dartgt said. The 727 is a great trans, you just don't need it behind a small block. I built a 904 for behind my drag/street 360 and I love how quick it shifts. Besides, it fit without the sledgehammer in the tunnel.