NOT THAT MY OPINION IS ANY BETTER THAN ANYONE ELSES BUT ACCORDING TO HENDRIX MOTORSPORTS IF YOUR PLANNING ON STREET DRIVING A 400SBC IT IS EXTREMELY IMPORTANT TO MAKE SURE THAT THE HEADS, STOCK OR AFTERMARKET, AND HEAD GASKETS HAVE HOLES MACHINED IN THEM MATCHING THE CYLINDER BLOCKS STEAM HOLES. ANY ENGINE THAT IS GOING TO BE PRIMARILY DRIVEN ABOVE 3,500RPM IT IS NOT NECESSARY DUE TO HIGHER CIRCULATION OF WATER FROM THE PUMP SPINNING FASTER ELIMINATES ANY AIR POCKETS IN STEAM HOLE AREA OF THE COOLING SYSTEM