Hi Tuck, I just stumbled on this on e-bay a couple days ago, I have no idea what the price of a drum would/should be.
https://www.ebay.com/itm/1966-1977-EARLY-FORD-BRONCO-TRUCK-CJ-JEEP-KOENIG-PTO-WINCH-PARTS/164761854127?hash=item265c9260af:g:nY8AAOSwxPRgRmmg
Regarding the binding you describe, it sounds like the worm gear is inhibiting movement, but not really sure what you mean by "it will only turn half way". If you dis-engage the shifter lever on the opposite side from the worm gear and its housing, it is linked to the shifter fork and should release the drum. Don't forget to pull the locking/release pin, it is spring loaded. Then check for movement by turning the PTO drive-shaft. If the grease inside is 50 years old as well, it probably resembles glue at this point and just needs to be re-packed. Also, whoever applied that paint you are cleaning off may have gotten some into the bearings and contact areas around the drum shaft or PTO shaft, binding to turn by hand but the PTO would not notice.
PTO's are cool and well worth getting to work, IMHO.