First thing I would look at is weight. Its free hp. What you have in the motor, every thing is very heavy. Were the heads ported using MP porting templates? Those pistons weigh a ton and probably about 9;1 comp. and the 590 MP cam sucks. But weight is your biggest problem and cheapest to solve. I had a 70' Challenger I did a full chassis on got the weight down to 2450 built a 451 low deck. Ported 906 heads with MP templates. Don't remember cam specs but was a solid roller with .625 lift and running LY rods. It ran 9.80 in Sacramento Cal. Not bragging, just an example of how much difference weight makes. If you're going to buy heads, don't waste your money unless you go with Trick Flow. If rebuilding bottom end think lighter pistons, forged and better rods. Scat makes a nice 4340 I beam rod. If your crank is a stock forged item, it will take the horse power. Just be patient and think things through. One more thought, a lighter car is much easier on your engine and transmission. Best of luck to you and your changes, and don't be afraid to ask anyone for advice.