I don't know what model craftsman I used to use, and it was long long ago, but you should be able to get a pretty good fit on the belt by examining the pulleys ("V" or flat or ???), measuring the width where the best would ride, and you can run a string or twine or something around it to measure length. Once you have that information, we may be able to help you find a belt. You could also go to the sears parts thing on-line, they seem to stock stuff like that for an infinite period of time. You can go by model #. On the tool post, it depends on what the swing is (distance from the center to the bed), but I would go for a QCTP set.
0XA is for small lathes, it's 60% the size of AXA. I've only seen it available from LMS. It's a great fit for a 7" lathe, yours may be 6" or 9" if If am not mistaken. Their website says up to 9", but if you have a 9", I would go with an AXA.
AXA up to 12" Most sites that list the size will say 9-12"
BXA 10" to 15" swing
Too big is bad because it gets in the way of turning larger parts. But, bigger is better, as it is more rigid. You will discover soon enough, rigidity is very desirable.
A call or e-mail to LMS will help you choose. There are other sources for AXA and BXA:
http://metalworking.mscdirect.com (site sucks, but it's the walmart of tooling. See if you can get a free Big Book)
For the QCTP, I would stay away from the cheap Chinese machine importers like http://ww2.harborfreight.com and http://www.grizzly.com/ I'm not putting them down, most of us have their mills and lathes, but not a good place for a QCTP.
The craftsman I used came with a lantern type, which I loathed:
We might off further advice if you post a pic of the crossslide and the pulleys + measurements of the pulleys and "T" slots if so equipped.
Good luck with your find! Those can be fun lathes.