'98 Tahoe Mystery Oil Leak

[awalts]

I have a '98 2-door Tahoe, and have some oil leaking from the motor. Due to a blown head gasket a little while back, I put in a brand new 5.7 crate motor about 5,000 miles ago. The new engine runs amazing and if it weren't for leaving evidence in every spot the truck has been parked in, you'd never know there was a problem. I have no check engine or low oil pressure lights. Both my inspection as well as the inspections from a few shops have shown that the oil is coming from somewhere in the upper rear against the firewall in the area of the oil sending unit. Underneath the truck, there's oil coming down both sides of the motor towards the back by the start of the bell housing and from up high. The amount of oil that drips to the ground when parked overnight is typically about the size of a silver dollar, so it's not horrible, but it adds up. Everything points to a slow, seeping leak. Before anyone asks, no, it's not contaminated. Just straight, pure oil. I've pulled, replaced, and re-sealed the threads on the oil sending unit and its elbow twice since that is the thing with the highest pressure back there, and that hasn't fixed it. The distributor gasket feels dry. I'm wondering if the "Form-a-gasket" crap that they use for the rear seal on the intake manifold is what's leaking. My next step is pulling the intake manifold to get a better looks and re-do the liquid gasket back there. Has anyone else run into this issue, and if so, what was the fix? Any recommendations? Thanks in advance!