If your engine is a 216 they have a regulator on the left side of the engine, This may be bad. Also the oil line for the rockers runs from that regulator thru the cooling passages to the rockers, I have seen where the line rubs against a push rod and gets a hole rubbed in it.

49 chevy 1-ton. It is a work in progress but it's getting close. 49 1 Ton Pics