I would get a bottle of leak tracing die at the parts store and put it in the oil. Drive it for a while and then look for the leak with an Ultraviolet light. With a fresh engine the clean oil can be very hard to see to determine where it is coming from. With the die in it and the UV light you should be able to find it pretty easily.
If it is on the outside of the bellhousing I doubt that it is the rear main seal.
Bill thanks for the advice! This was my weekend plan. Just trying to get people's advice on potential spots that are prone to leak on these motors.
I put it on my buddy's lift this morning before he opened up (owns an exhaust shop), and it's definitely wet mid way up on the bellhousing and dripping down. I noticed some RTV silicon (or similar product) at the rear of the intake manifold. It was definitely put there during the engine rebuild because it has been painted over. So, that's a potential location??
There is some leakage on the drivers side, but not nearly as pronounced as the passenger side. What's weird is none is dripping on the exhaust. I don't have any smell of burning oil, ever. But it definitely leaks more once warmed up. I notice when I start it and back it out of the garage, no drips, but after I come back from a drive, there is noticeable drips on the driveway if I don't immediately pull it in the garage over some cardboard. It runs great, so I don't think it's a major leak, for now, but I want to get it squared away before it becomes an issue. I just hate leaks!!!!!
So, I think the rear main can be ruled out. The origin is higher up. The valve covers have leaked/weeped in both Mustangs I've owned, and my dad's Willys, but not this much, so I am leery to rule them out. But, for it to leak enough to sling it down the undercarriage lends my thoughts to something that is pushing out more oil when under pressure and warmed up. The valve covers shouldn't be under pressure, right? The PCV valve is on the passenger side cover, and routed to the manifold, which looks to be correct. It does have a T fitting and splits into a much smaller tube that goes into the firewall (not sure about that....!!!). But, with it freshly rebuilt, I don't suspect the PCV valve to be the issue.
Thanks again everybody for the inputs. Looking forward to finding this pesky leak! I like the underside just as clean as the top side!!!