Having seen this brought up I will put my .02 in. A buddy of mine rebuilt a 383 Dodge motor one time for his van. He lived about 2 hours away from me and on his maiden voyage down to see me he called about half way with problems. He was graduly loosing
oil pressure at highway speeds. If he drove real slow and kept the rpm's down it seemed to be ok. I took off and met up with him to see what we could do.
After we went through all the normal questions and dumb looks at one another we decided to drain the
oil and have a look at it. We bought a 3 gallon drain pan from the auto parts store.....damn near filled it up....lol. He had forgot that the dip stick was the wrong one. He also forgot how many qts he had put in initialy. He filled it up untill it registered on the stick. The crank throws were cutting through the
oil and severly airating it. We got the specs on proper oil amount from the parts house...filled it that level and off we went. Didnt have a lick a trouble after.
Just something to think about and possibly eliminate.