If I were you, zksmith1, I'd hold on to your 2 antique toilets if at all possible. I have 3 of them in operation and several in storage, in what I jokingly refer to as my "Antique China Hutch", all of which I cleaned and rebuilt myself. They are the best!!
I am familiar with the Crane SAXON, also SAXONET, as well as the "Standard" TIFFIN. I have 3 of the TIFFIN tanks that you mention as well as 2 of the TIFFIN bowls, one made in 1926 with a "spout" in the flush rim at the back of the bowl, and an identically shaped bowl made in 1929, stamped TIFFIN in the back, but marked "Standard" EJECTO on the area in between the seat post holes, and the spout replaced with a jet. "Standard" EJECTO was completely redesigned in the early 1930's, and then "Standard" MODERNUS was introduced and made for a long time.
You might look at the DEA Bathroom Machineries website and click on the "Specialty Plumbing Parts" button. They do sell the 2-inch flush elbow that comes with the nuts and washers that you would need. They may also be available to you locally in a plumbing supply store.
Oddly enough, I am able to get them in a hardware store, but only a few of these stores carry them. I think I paid around $20 for the last one.
I also have a friend who had the same problem as you are describing. He called a plumber who completely rebuilt his toilet, including the elbow, a new spud fitting in the back of the bowl, and all new tank parts except for the original flush handle.
Hope this was of some help. Good luck on your repair!!