Gotta agree with Rod on this one, with all the parts you're buying, I'd go alternator.
I've got one 5000 got converted about 3 years ago, it's great. when it still had the generator, that tractor would need a new regulator every 5-6 months...or whenever hay season rolled around and I needed it daily.
But I've got another 5000 still has the genny, and that one has not been worked on electrically in 2-1/2 years.
Got a recently acquired 4000 that's not charging...nothing even if I full field it. If all it needs is brushes, I'll try the generator for a while, anything beyond that and it's getting an alternator.