Had 1968 340 engine rebuilt and run on dyno. Engine ran beautifully with 60 psi oil pressure. Ran 5 pulls to dial it in. When I went to dump oil and change filter, I noticed oil filter was bone dry. I pulled oil pan, windage tray, oil pump and rear main bearing cap to see if any plugs were missing causing bypass to occur. Everything looked to be in place. Any suggestions would be appreciated. Thanks...... Mark