Ron,
The early heads exhaust ports are tiny and I'm thinking that they are really killing power.
Anyway, for 500HP your going to need to basically duplicate my short block. Sleeve, rods, forged pistons, head and main studs. Get a '06 up head and port the head - most of the work needs to be done on the exhaust side. Then you need to decide what you want to do for cams - run stock or get custom billet cam made.
