I haven't used the Canfields, but I know a few that could not get them to work well, could have been the combo's they had. If I was in the market for new 23* heads, Darts castings are the finest and you can get their non-CNC to work well with minimal work. AFR CNC's their heads as a standard practice and also work well. Just remember when you look at the larger runner heads you have to go to offset shaft rockers. What is your 408 going in and what is your ET goal? Or street? Let me know all the rest of the parts you plan to use, trans, converter, gear ratio, vehicle weight.