I was by Sampson Racing Engines earlier today and saw a 4-Weber downdraft carb setup on the desk. I asked if it was for a SB Ford, and Dillon said yes, '66 GT-40 motor in for a freshening. We went back and he showed me the legendary heads that Dan Gurney's shop made for the 5.0s back in the day. He said this is his favorite motor to build out of all his customers. He said the pistons were just a little tall on the last build and I could see that they were making light contact with the low side of the chambers from high-rev downshifting. He's going to install about 0.010" more head gasket thickness and see if that clears it up.