Every generator I have fooled with that had the engine coupled dircet to the generator,had a tapered crankshaft PTO....some belt driven ones had the usual straight crankshafts though..yours probably will be a tapered version--its possible to buy or make an adapter to convert it to a straight PTO,but its probably not going to be cheap...a bearing supply place or machine shop are two places to try..you'll have to know what taper it has though,and getting the engine off the generator isn't always possible without damaging the generator..
I would just leave it as a generator ,if you can get it to run and put AC current out...
I would just leave it as a generator ,if you can get it to run and put AC current out...