What yr is the truck block? The earlier 318's are known for having thick walls. 4.070 is equal to a 340 +0.030.
I was stripping the k-frame out of a '74 Valiant a few days ago and the driver's side mount was four bolts... I don't think I'd ever come across that before. I thought it was unusual, but now after your question, I gotta go back and find out more about the block, just to satisfy my curiousity.
Mike in FL
