Re: looking for a manual trans for my 460
The T56 would be strong enough and a great choice.
I just don't know about Ford Big block Bell housing compatability. If you have a setup for an auto then you will need to find a bellhousing and flywheel for the bigblock. They probably aren't so easy to find as most will have had autos behind them, then you will need to perhaps adapt it to suit the T56.
Perhaps some performance shops may sell a new setup all suited to the T56.
71 429SCJ Mustang