Haven't had any luck with the pumps, it was rebuilt when we bought it, lasted a couple years, then gave up, exchanged it for a rebuilt pump, it lasted one year, exchanged it again for another rebuilt pump from another source and I believe it's on it's way out.
Both shops told me parts were getting hard together for this particular pump and I'm a bit fed up with it.
The engine is alright otherwise, except idling at 1100 and full tick over at 2700rpm doesn't make me very happy. Plus it's a bugger when starting in the cold even when plugged in.
The 5.9 I'm thinking of came tuned from the factory at 110hp, the allis engine is supposed to be 95, so i can't really see any problems.
I won't be trying to push the combine any faster.
Those 3.9s also don't seem to like the cold in my experience, at least Ive had better luck with the 5.9 in cold weather