I just had to measure this, actually.
http://www.cnczone.com/forums/1045602-post1.html (PDB questions.)
The 1100 drawbar is 11.5" long from shoulder to the end of the threads.
The drawbar for the 1100 with ATC is about an inch longer to account for the spring stack.
I don't have any numbers on the 770.
One other thing. The drawbar machines easily. I was able to use my 7x10 mini-lathe and a carbide cutter to modify my old drawbar. It cut like butter. So if the Tormach drawbar is too long, you can trim it down and re-thread it.