MAPP gas will do nothing other than burn your hand. The bike managed to input enough force to bend the entire subframe assembly - I raced for years; bent subframes were part of the deal. The best way to straighten is to use something like a 6' length of 4" I-beam, chains and a porta-power.
You can't hold the bike securely enough to simply stick a lever in the bent bits and pry - you need to fasten a rigid beam to the steering head and rear of the subframe and apply pressure at the juncture of the frame and subframe. It's a dlow process that doesn't use brute force so much as the correct application of force.
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