I just bought an 89 Pete, engine has been swapped to a 3406b 8TC***** engine. Drove home had 60psi for a couple hundred miles. Sat a couple weeks then took off to go load got down to shipper and idle psi was about 18psi. Brought it home did rods and mains with a new oil pump and new o-rings on pickup tube and oil supply tube. Also thoroughly cleaned screen on pickup tube. Took off today. Oil got hot and dropped to 22psi at idle. Brought it back and checked guage, put a new guage on hose for Factory guage same reading. Put guage on one of the plugs in oil galley on other side of engine and I have a 10-12 psi difference from left side-factory guage port, to the right side-oil galley plug hole, reading higher on right side...and I can't find anything about why it would do that, help please????