I'm new to this thread, sure hope your hair grows back! You must have it all torn out by now.
I learned something about 340's. My '74 Challenger(orig 318) has a 340 installed by previous owner. It's a '73 340 block with parts he got out of a blown '68-340. I don't know which crank is in there-my guess would be the '73-so it is proabably a cast unit, unless the '73 motor came out of a manual trans car?
I still have the stock 318-issue 904 tranny, I had a terrible vibration when I drove it but then I had the engine looked at and ended up getting the valves/heads redone. It has a lot better power now, but I didn't get to drive it but 10 miles before parking it last fall. I am going to have to try to figure which crank I have for sure and check out my HB.....I might be in for the same things as you.
Anyway, thanks for putting all your trials and tribulations out on here. It may have saved me a lot of heartache. I thought all 340's were internally balanced.