Link may not work...
the "take off" on that trans is just an adapter to the output shaft direct to a sprocket that then runs out to the yarder, most times these are missing for some reason? but I don't see why a couple pillow block bearings and direct coupler to the output shaft won't work, as for gearing down most of that is achieved by the sprockets sizes on the drums, sprockets are fairly cheap and easy to machine the ID to whatever size you need,
Sprockets in general are "LEGO" parts, find the correct chain pitch and tooth count you can probably find what you need through McMaster Carr or one of the Bearing Shops in Everett. (pacific bearing?) as for shaft work, maybe Drivelines NW, they may even be able to source an output shaft, but for sure the correct coupler to your intermediate Jack shaft. Probably going to be more then a little custom machining involved... nothing major but you'll need some one with more then the harbor fright bench top lathe/mill combo.
I have seen some that had a sprocket mounted direct to the jack shaft... how wise this is I'm not real sure as the trans casting isn't really designed for side loads like that.
As for the Motor... its a Ferd, throw some ATF in the spark plug holes, wait a day or 3, clean the carb, give it 12v and it will probably even run, the trans might be seized tight too though... Really a funner option would be to stick a Cummins 4bt and an automajick trans on there... but purists be purists lol.
