[Mike Dozier]

Since 429s fit under the hood of 71 Mustangs,
a 460 should fit under a GT40 clam provided
the mounts were welded in the proper spot.
Problem I'd think would be the trans.

First you'll have to do some engineering to mate it $$$,
and I doubt you'll be able to use an inverted G50 since
I'll bet the 460 has to be set lower in the chassis.
So unless you want to "baby" a trans, you'll be looking
at $ 10k tranny or more. But hey! If that's what you want,
I say do it! It's your car and would certainly be cool.

As we've seen, given enough time and $$$, amazing cars can be created.

MikeD