That's exactly what I was told by all except for a guy that used to be on a top fuel (reworking 426 hemi's) back in the day. He said that it will either run really well or not-it was a gamble. The heads were reworked professionally (Heads by Paul-Denver) What happens is that it supercharges the mixture due to the smaller heads. It ran really well despite the 305 heads. Flat top pistons.