A set of oval port heads will run fine to 6500 but that is pretty much it . The rectangular are for high R.P.M. 6500+ they move huge amount's of air and fuel. It's your choice . Your not going for gas mileage anyway if your in the big -block forum .I have a wife also that would be mental if I bought a 8-71 out of Jegs . You are not alone my friend . Anyone that say's there wife isn't involved in there garage is full of B.S. or they are about ready for divorce.