I finally just got the culprit cylinder head out of the car. Upon removal I noticed the head gasket covered the rear coolant passage from the block and where the center coolant passages are supposed to be on the pre 73 ish heads. This cylinder head is missing the center coolant passages as found on the later heads. I could tell the cylinder head gasket is not factory so I am assuming someone just threw on some cylinder heads they had. The pushrods are capped (non oil through) and noticed the outside of the pushrods were dry, however wear is very minimal on the motor from wall scoring to pushrod wear. This is a 1 family 4 generation owned car since new and I find it hard to believe they took care of it only to put later heads on if knowing of the coolant risk. What say you small block experts? Does this mean I can use any cylinder head on the 69 and just swap the rocker shaft over?