The last two stuck stems I had ( Centurion Le Mans & Trek 460 ) were removed while the forks were still on the frame, I just turned the bike upside down. The Le Mans I used Evapo Rust and the Trek I used PB Blaster and a little Evapo Rust mixed in, I would tap on the fork with a soft face dead blow hammer like a tuning fork and let it vibrate. Both took about a week & a half but it was so cold I wasn't working in the shop and would check on it about every two days.

Glenn