I've been on the lookout for a 450 or possibly a 451 snowblower for my 1872. I had talked with a guy in PA about a 451 he had posted for $855. It would have been a 4 hour drive for me and he would only come down to $750 so I decided to pass.
I'm glad I did because a guy 30min from me posted a practically brand new 450. He got it with his 1872 back in 1992 and it's been in storage ever since, he never used it. I managed to pick it up for $390. It's in really great shape so I think I did ok. Of course, pictures...
It turns free. I think the first step is repacking the gears.