new heads or rework old ones?

[PWR_RYD93]

I agree, sell the Holleys and buy some AFR185's. The difference in price will be less than you would invest in larger valves, cutting the valve seats, blending the bowls to the seats, porting runners, etc. The Holley heads are very good heads, just a bit too small for 347 cid. You should easily be able to sell them for $750-800. Your motor will scream with a set of 185's if you have the right supporting parts (intake, cam, T.B., MAF, exhaust, etc.).