i have a 69 f250 and had rebuilt the 390 about 10 yrs ago and my friend and i were travling down the freeway and some collage kid wanted to race or try he had a newer f-150 that he thought was fast and he kept up for a while until i shifted the c6 into passing gear at 80 and spun tires he finally caught up at the rest stop and got really ticked when he saw the stock 390 with a two barrel those two barrels work bgood but really suck gas when you hotrod them.the truck just purrs now,must have blown the carbon out.