Confederate,
I installed a 460 in my old 79 F150. First thing you will find is that Ford never put a 460 in the F150, so you will either have to make or buy all new brackets, motor mounts, oil pan and custom headers. Back when I did mine the only decent headers that would work a set of fender well headers, which you may or may not have to modify brake lines, fender or steering linkage on the driver side. I bought a crate engine from Jasper Engines that was supposedly putting out 375 to 400 HP and never changed or modified the stock axles and they survived for over 3 years.
You have to be careful with marine engines, they are typically built to run at higher RPM's and sometimes run in reverse rotation. I think somebody already mentioned they have low compression and most of the torque occurs at the low end, which is good for crawling but sucks for daily driving. If your just wanting to swap the engine in and go you need to try and find one out of another truck. Another thing to consider is that a 460 is very big and very heavy. Personally, if I was to do it again I would consider using a 302. Their are so many aftermarket parts for these engines and they can built to handle up to 500HP.
But then again there's nothing like that big block feeling when your smashing the pedal down to the floorboard ;D