Brent,
I tend to agree with these guys. Throwing more new parts at it might not be the most prudent thing to do at this point. IMHO Time for some real root cause analysis by a qualified FE engine builder. If it were me, the motor would not go back in the car until it had been run on a stand for some time, and thoroughly checked...
What might seem like the fix right now, might not be, and you could end up right back at square one again; and even more flustered.
When Tom at FE Specialties blueprinted my motor, we ran it (on the stand) for over two hours checking the
oil to the top of the rockers, shafts, top of the heads, drainbacks and more. He will not build motors any more without doing this because of problems just like this and due to the variances seen in parts manufacturing and quality control issues.
I don't know if you've talked with Tom Lucas or George at Gessford a bit more, but I bet an experienced, well-trained eye will find your problem in less than one hours worth of shop time.