Hummmmmmm! Leaks/burns 2 qts. of oil in 50 miles @ 20 years and +-29,000 miles? That's a lot. It's true Ford doesn't manufacture the engine as a complete unit anymore but their OEM website shows that OEM rebuild parts are still available for the 460 in various oversizes. I wouldn't let anyone talk you into a complete engine rebuild unless they can show you major engine components which have inherent major faults or wear. (valve stems, valve guides/seals pistons, piston rings,heads, block, etc.) Those parts are generally fixable by any good engine rebuild shop or available in the aftermarket.
Chum lee