The last I had to do with one was about 10 years ago. Parts were a bit hard to get back then. They were based on the 1065 SP, so parts which are the same as the 1065 should still be available.
Ours was 1000 rpm PTO. But I know of someone else who ran one with a Chamberlain 4480 tractor, as far as I know the Chamberlain sedans only ever had 540 PTO. So I don't know what they did to make it work.
Quite inventive the way that the comb folds around behind the header for transport. Good sized box too.
Yes it looks like a good design with good capacity! I am looking to replace my john deere 7720 which ran out of oil! Not worth money spending to fix these days!
Have a john deere 4640 tractor 1000rpm and so looking for options to harvest 300 acres per year so thought the 1051 may be an option