Dynobite:
With 5 mths and 1800 miles on the motor, you are going to be hard pressed to get these guys to make good on the build. I been to that "leak" show so many times, I should get a PhD in leak technology. I always figured I pissed off the leak god and he's getting even for all that naughty stuff I did in the past. Anyway; I wouldn't pull that motor for a stupid leak; and i really, really hate leaks. My instinct says you are "missing it"; cause we have all done that too. It is REALLY hard to see some times.
Having said that; I'm assuming your a little like me and "prefer" someone else do it. I am too old, tired and cranky to crawl back into that engine bay. So here are "MY" discovered leaks at one time or another on prize leaky FE:
Rear corner of valve covers is culprit 90% of the time. If you pulled those valve covers more than 2 or 3 times and didn't change the gasket; you can bet one nut it's leaking. The gaskets compress and harden. OR, you didn't retork them a couple times since build (25lbs as I recall). And it weeps out and down the back corner to the bell housing and off the flywheel teeth (if there is no inspection cover). It looks like a rear main leak.
Your odds are even worse if you have aluminum Edelbrock heads. I know; I gottem and they're garbage. Edelbrock considers .060 out, (with-in "their" spec), so the gap where the head & block mate, leaks the majority of the time. I milled mine flush cause Edelbrock wouldn't make good on them. It looks like a rear main leak.
Rear of manifold is next in line. Again; really hard to see leakage some times. It takes heat and when you shut down and she cools, a very fine stream leaks from the corner of the dam where the head & manifold gap is filled. Not sure if you corked or dammed yours. It looks like a rear main leak.
Remote
Oil Filter adapter on block has 1 bolt not tight and it travels on the lower side of the block and drips off bell housing when you stop. It's a puzzling trip from the front to the rear. But your frame rails will never rust.
Cast Aluminum pan has a teeny, weeny, tiny scumbag weld crack you can barely see and it leaks after she heats up good. It travels straight back and drips off the flywheel but it looks like rear main is dripping. That same pan has the drain plug thread hole drilled cocked so the plug can't seal flush against the brass washer. Naturally; that's Canton quality too. That said; they did replace the pan and for 300 bucks they ought too. It's the $1000 of aggravation they couldn't compensate for.
Rear breather on manifold leaks off the back of manifold and down around bell housing and winds up in the vicinity......... of a rear main seal leak.
Ya ready??....... Distributor shaft hole...... Yep; O ring was bad coupled with back pressure in the galley. HOWEVER, did NOT look like a rear main leak. It looked like timing chain cover.
SOLUTION with path of least resistance: I am going on the basis you don't want to be bothered doing it yourself and I fully agree with you. Check in town for a station with a decent mechanic. Tell him to steam, clean and wipe that block down squeeky clean; put an ounce of dye in the
oil; Take it out and drive 30 minutes. Bring it back in and put it UP ON THE LIFT; Put the Black Light on it and see where the
oil is squirreling out. Probably cost you $100/150 bucks and save yourself a $1000 worth of aggravation. If it's one of the above. Pay HIM to fix it. If its the rear main; give Southern some free publicity although 5 months is still a stretch to go after them.
Good luck with it; I empathize with ya.
Bernie