Had two row unit gear boxes on a NH 974 corn head fail at the same time Friday night.   One locked up because a bolt came loose enough to lock up gears, no damage.    Other one had bearing out and of course local dealer didn't have the bearing because "The last one we sold was to you two years ago".    Tired of these guys never having parts and am wondering about the practicality of just getting a row unit or two from a salvage yard and replace when needed and fix later.  

Overall, the head I have is in really good shape,and outside of chains, sprockets, and deck plates I've only had one other bearing go out and there was a gear out in a gear box when I bought it 9 years ago.

I don't want to buy another head, so I'm wondering how many people keep extra units on hand and swap when needed.