I had a T-176 behind an AMC 360. No issues, and I wasn't easy on it. Now with the 5.7 install, I went with an SM465, it was given to me. Hard to pass that up. I did have to spring for the adapter for the d300.
For ME, the 176 was a better around town type trans. The extra gear between 1 and final comes in handy. With that said, the tremendously rugged feel of the 465 feels MUCH beefier than the 176. Finding the right gear is for certain speeds can be a minor issue. I'm either reving the engine a bit, or lugging it, which isn't good. The low/granny gear of the 465 comes in VERY handy.
IMO, if you are not going to flog on it and drive mostly around town, find a t-176 with a d-300 already mounted to it. Price may be better than getting an adapter. If you like to beat on it a bit, want a rugged trans that you will probably never have to take apart, do some wheeling and would like the low first, go with the 465.
Only you know your driving style and terrain.