Sorry, I don't have any help on the specific machine and change gears that were originally supplied, but you should be able to figure out the generalized solution.
Change gears establish the relationship between spindle rotation and carriage movement. Carriage movement (per rotation of lead screw) is determined by the lead or threads per inch of the leadscrew. That will be only one of a small range of threads 4, 6, 8 or something, so you can check your leadscrew, then look for another make with the same lead and see what gear sets they supply. Whatever that is will work for you.
Manuals for other lathes might be more readily available, or armed with leadscrew pitch information some other user can tell you what his lathe has.
"In theory there’s no difference between theory and practice. In practice there’s a lot of difference.” Yogi Berra