I prefer the 4.25 or 4.3 stroke with BB Chevy rod sizes in any of the BB, 400 or 440 700 HP is not hard with the right heads, intake and camshafts and rocker gear. As already said have any block sonic tested before buying it, you want .150 minimum on the major thrust sides after boring for a compression motor above 8.5 to 1 N/A