I have a 351C in my 67' and a reliable source (as he restores these kinds of cars, including cougars) has told me some interesting info on my 351C. I rebuilt my Cleveland with a high volume Weiand water pump to avoid over heating which is a common occurrence in these motors. My source tells me that the high volume pump will likely blow a hole in my heater core under the hood due to high psi and I DO NOT want a coolant leak in the interior. He told me to restrict the flow to the heater by going from the factory 5/8's od size hose to a 3/8's od hole going to the inlet of the heater. Has anyone else heard this and how did they do it? Thanks for any info.