What needs to be done to get 500 hp out of a 460?

Trying to get 500 hp out of my 460 for an off road rig. The rig shouldn't see to many high rpm's but will occasionally when I feel like beating in against the rocks.

What I have so far D1VE block, D3VE heads, Edelbrock 7167 cam and an Edelbrock 7166 performance intake. I know I probably news some aluminum heads but I really don't wanna spend $1800 on a set

I plan on running propane (roughly 100 octane rating, for those unaware) and may need to get a dual carb intake since the highest propane carb I know of is 625 cfm.

Read this it will help you http://www.429-460.com/t121-big-block-ford-horsepower-chart-info-gathered-by-djohagin

Yes you will need a dual Impco 425 mixer setup. You will be able to get to the goal pretty easy with the extra C/R that the propane will support. A good flat top build with those D3VE's properly ported and a cam to support the heads will be the ticket. I have seen an adapter that was like an inverted tunnel ram top that held two mixers and bolted on top of a standard 4bbl intake. I have no idea who made it, or where to find one though.

that engine build page is good, but doesn't state anything about pistons. what should I use, flat tops?

for propane more compression is better as well as valves and seats made for propane. In my findings you need 600hp on gas to make 500 on propane.

Cooter,
Back in the eighties there was a gentlemen from Indiana who ran a Buick somerset in super-gas. Later he went to a dragster. The car was called the "Natural-Gasser".
Supper-Stock & Drag Illustrated did a big write-up about the car. It was mid-to late eighties when the article was written.
Joe Henlina, the owner, I beleive his name was, did all the fabrication and set-up on the intake. He worked in the propane field at the time.

For Great source of back-issues try www.dragworldusa.com Larry is a STAND-UP guy and great guy to boot.