Probably already checked but most of the aftermarket oil pan bolts are a touch longer than factory and will bottom out and not compress the gasket. Found this out my hemi. I thought it was rear main also. My easy solution was to add 1 grade 8 flat washer to each bolt.
My block has studs for the oil pan, so my pans tightened right up against the block. Thanks for the heads up though.
Does your motor have main studs also?
If so look at the rear of the oil pan and the oil pan gasket under the rear main seal and see if the #5 main studs are touching them
If so yonu may have found your oil leak before removing the rear main seal holder again
