Great information. My 4.1 build is mostly street driven, and don't plan on full tilt output. I hope you can source a piston. I am looking myself, I though of Earl first, then I guess follow some leads here unless I stumble upon something different which I'll post.
Were do you plan on getting your rotating assembly? Sucks about the spun bearing, but like me stuff like that leads to more moeny spent and more power, lol
I run a lock up converter. I'd have to dig back into the tune to check my flags, its been some months since I've messed with it since the engine is hurt.
Sounds like a cool project, I hope you can make some headway on it. I don't have any real advice for the trans swap though.
Also, the willies would be great, I have a 63 willies truck with the flathead six, my mountain truck, love it!