I've got a couple Trek 760 stuck stem stories.
The first one was an '84 that I picked up for $100. I bought it at night without having good enough light to look it over really well. I could see that it had some rust issues though. But what the heck - a 760 for $100? When I got back home with it the seat post did come out with some effort. I proceeded to take it apart taking note of the Superb Pro parts, corroded, pitted, Superb Pro parts. Also poked around at the rust on the top tube around the cable guides. It was rusted so deeply I poked right through to the inside of the top tube! Oh well. At least I should be able to save a few components. Well the stem was stuck. Bad. Soaked it for weeks with PB Blaster, tried heating it and submerging it in ice water repeatedly, inverted the frame and filled the steerer up with coke, and let that soak for another week, and it was still stuck. I really wanted to salvage the Cinelli stem, and the fork. Finally one day I wedged a 2x4 in the fork of a tree and placed the fork over it so it went between the blades of the fork right at the crown and twisted so hard I'm lucky I didn't injure myself, when something finally gave way. One of the fork blades broke/ bent right at the crown. I still have that frame. Maybe I can still get the stem out. It's hard to admit defeat.
The other 760 I bought as just a frame knowing the stem was stuck (can you believe it?) When it wouldn't come out with soaking and moderate force I just cut it out with a hacksaw blade. Sawed it off about 3/4" above the headset and made two slits in the inside of the stem. Then squeezed it, and it came right out. Took a little over an hour. No damage to the fork...