[Dark_5.0]

If you are revving past 5500 with the stock cam and heads you are way out of your powerband.

My set up only pulls to 6000rpm's

If you get the heads ported and replace the weak valve springs and get a cam you may get there.

For what you are wanting to do I would just go with some good aluminum heads. You can find good deals if you look around. I found mine for 600 bux.