For starters, are you talking about 600hp at the rear wheels or flywheel?
What kind of transmission?
The easiest way to make that power would be to toss the cam, rods, and pistons, send the heads to scott at reincarnation automotive and have them ported, buy a 4.5" stroke steel crank, rods, pistons, and run a victor dominator intake with a small dominator carb. Have the guys on the 460ford.com forum spec a cam for you. If you want to take weight off the front end, put some blue thunder heads on it...or some TFS if you like...or the new Kaase CJ heads.
You'd have no problem hitting a 600flywheel number with that combo on pump gas and wouldn't have to spin it past 6000rpm to do it.
Take a look at the engine build section on the forum mentioned for known combos.
Like this one:
http://www.460ford.com/viewtopic.php?t=629
That's a nice mild build that would last. More power is just a cam and induction change away.