@f-bird88 I know this topic is about 2-3wks old. You mentioned something about poor man's racing heads. I was breaking down a motor this week end that came out of this 73 c-10 short bed before I put the 400sbc in. The casting number was block 3956618 & heads are 3932441 what info could you give me on this. I know you said in a comment back that porting these heads on a 400 would scream. I was going to rebuild this motor as a street deal for my 73 vega any comment would help.