If it's worth it depends on you. Are you building the car to keep or sell. Many will make the arguement that this can devalue the car. If you are keeping it, who cares?

A few companies sell motor mount kits to swap the 460 into fox bodied cars (including the Mustang). It should be pretty much a bolt in swap. The only issue is rewiring the engine compartment for the engine and induction being used.

As for the 302 vs. 460 issue, as the saying goes, there is no replacement for displacement.