Is it a 53' engine? Some engines had a full flow filter, and some had a bypass filter. if it's a full flow filter, a block in the oil filter or lines could be causing a prob. but that wouldn't be a problem with the bypass filter. (although it would definately be a prob in the long run)
Did you have your block boiled out when it was rebuilt? Just trying to eliminate a blocked passage as the culprit...
Did you plastigauge your main bearings??? if there is too large of a gap there you won't develop enough pressure for the oil to make it up top.
You might check the clearance between your oil pump screen and the bottom of your oil pan. Too close and it will restrict oil flow
