OK. That is the middle model, made from sometime between 1944 and 1947, and 1948. A new model was made from 1949 until 1961. The reason that the first year is indeterminate is that Sears didn't publish a Power Tools catalog from 1944 through 1947, and there is no way to date an AA lathe.
Your idea sounds good but has drawbacks. First, availability of accessories for 1MT is not much better that the availability of ones for 0MT. So you would probably want to go to 2MT. I think that the diameter of the tailstock ram is probably the same as the spindle, 1/2". The diameter of the small end of a 2MT plug is 0.572". So the entire socket would have to be external. If you use something like 4130, you would probably want at least 1/4" of it solid. The diameter of the large end of the hole is 0.700". The depth of the socket is 2-39/84" (2.6094"). So the external part would be at least 2.8954". This would reduce the distance between centers to about 9" or a little more.
If you can find the accessories that you want in 1MT, the situation might be a little better in that the small end of the 1MT plug is only 0.013" larger than the large end of the 0MT socket. However, the ram would be weakest right at the end of the 1/2" dia. part and therefore, even with the 1MT, you would be safer to put the entire socket external.
Also, in order to be able to eject an accessory from the tailstock ram, the ram can't be solid at the end of the 1/2" portion. And you will need to also make a new and longer feed screw.
I suspect that you would be much better off to try to find a 618 (or 101.07301 or 101.21400 or 101.21200) tailstock and base cheap and have the base modified to fit your V-bed. This would give you a safe 1MT ram.