Go to the 460 forum as suggested above. There are some really knowledgeable people there and you can trust that if they recommend a place to go for parts, you will not be ripped off and what you buy from those people will actually work as stated. I for one would take a long, hard look at a 502 stroker setup and use a set of fully worked 1968 1971 C8VE, C9VE or
D0VE cylinder heads. Correctly set up, your engine will give you reliable and torque figures in the 500 plus range.
A well built 460 with aluminum heads and a decent cam will easily surpass the 500hp marker and run for years. Remember though that with that kind of horsepower you need a special
oil pump (FORD SVO / SVT / SCJ) and a mix of other items that enhance the longevity and reliability of your engine.