so your question is to stick with the stock x heads or swap you new ferrea valves to new eddy aluminum heads? The stock eddy head will flow a bit more that stock x head. You will need different head bolts to change to eddy heads. Also if you run hipo exhaust manifolds they can hit the eddy head. Header flange will space it out enough to fix it. Also the alt fitment can be a pain on the eddy heads. It can be more difficult to run bigger roller cams on sbm iron heads, not enough installed height. You can't really cut the valve spring seat, you can increase the total valve height but then you're stuck with what to do with the rocker shaft height. I have run both, but because of the class I run I have to run the x head. I you do decide to change to aluminum and want to sell the x heads let me know. Sorry to highjack the op. But to the original poster, a big variable in cost is the porting to "get everything to flow together" IIRC my porter charges $90/hr
