Mark, if it is indeed as loud as a diesel, I am not sure I'd be hammering on it, or driving it at all
However, loose flywheel or converter bolts, rod knock, piston clearance, wrist pin issue, pistons hitting the heads, if much lesser, lifter preload issue, PS pumps can make some funny noises, fuel pump, etc, if a Motorsports fuel pump eccentric they can hit the timing cover.
I am not going to Massachusetts anytime until maybe early next year, but man I wish I could go inside and do some looking to try to help.
ON EDIT: I just listened to your video, it sure sounds like the rear of the engine. It also sounds reciprocating to me, not rotating. It was hard to compare the Sept and October video, but some questions
1 - How did you determine pushrod length and did you end up with more than one length pushrod?
2 - Which rockers are you running? Did you check clearance for the cup if adjustable?
3 - Did you check clearance at the rocker baffle (it sounds lower than this to me, but there can be interference there)
4 - Have you had the valve covers off to see if any bent pushrods or collapsed lifters?
5 - An FE stroker only slows about .250 of skirt at BDC, but did you notice any scuffing when you checked for clearance?
6 - Did you check all pistons for clearance to the crank at BDC?
7 - Any chance there is an exhaust leak hiding in there too? I know not THE issue, but I hear a few things
To me I hear a definite valve train noise that is consistent in both videos, I also hear what I think it piston slap in the Oct video, but I think you need to verify preload is correct first.