I have a have a 1970 formula 400 ram air car. My block is yz datye stamp a070. i have both #13 heads and #12 head. The car is auto with a/c. Phs docs say either head. Peate McKarty chart says the same. Wallrace racing chart different. I heard stories that Peate made a mistake when he wrote the book but can nort find it any where. Im tying to be correct numbers matching. What heads should I run? Can anyone send the link to clear this confusion up?