Just pulled the sole out of my 1978 MA20. Came out pretty easy. I cut the hull flange off with a circ saw all the way around, pulled the tank, used a hole saw to cut a hole in the fwd end of the tank trunk and also in the deck just fwd of that so I could put a strap through and pull it with the forklift. Came out without too much fuss. Then the flanges came out just by ripping them off the hull sides by hand.
Raising the whole sole 1" and building new sections for the sole. The old sole was very wet and very heavy, probably 300+ lb. The new sole is 75% Divinicell foam and will be 1/2 the weight of the old one. Reducing weight was a primary motivation for my project. Realistically I think building new is about the same amount of work as re-coring, especially if you want to raise it up. And, its new and better quality as well.
Some pics for reference:
https://drive.google.com/folderview?...Hc&usp=sharing