They are quite similar. Early Tonti's are the same, as far as I know, up to the LeMans 3, which had a longer swing arm..from memory.. always dangerous with me. Then the steering neck was longer from the Cal 2, I think..swing arm length changed again, maybe other changes like a wider swing arm on later models. As far as I know, though, the frame rails stayed consistent, so yes, the frames are similar.
Take all this with a grain of salt if you are planning on making an early LeMans out of a Tonti frame, though.. the information is out there with enough research.