Speaking of tires, there is a lot to gain in terms of mileage with the right ones.
Since you are doing a regrind, maybe talk with Oregon about a dual pattern cam to help crutch the exhaust with your stock manifolds. Are the manifolds 318 or 360?
Whoops never mind about the regrind comment I see you have a comp cam already.
If you do nothing else to help compression at least run the Mr. Gasket .028 head gaskets.
Also another question- is your converter lock up or no? Obv 904 l/u would help mileage.