Im glad its narrowed down. Im new to all this and just getting to collecting and getting a few running for now for the kids (and me). The amount of work done for restoration you guys do is amazing.
The little bit ive noticed is the frame has the square mounts for the rear versus the triangle in the MT bike flier pict posted above. They have been cut/broke and the old tabs welded on the new. Also where the scrub brake mounts has the oval tabs similar to the MT. Seems like either way the rear sprocket setup and mounting is the same.
Before i go much further i may as well see if the Tecumseh OHH50 I got with it runs. Seems like a lot of motor for it..
Sitting side by side of the Bird i just picked up the frame is about 4" shorter..