Sweet little unit..!! Could be those Cole hoppers just happen to be the same size, as that unit used before. And those definitely aren't Cole style plates, at least that I've seen, and that was only 2 styles.
Personally, I'd be looking real close on the cast iron parts, for part numbers. Seed hopper bottom assy., seed drop foot/shoe, things like that. Then use Google to do a search on those part numbers. It may lead you to a parts list somewhere.
It looks a bit rusty, so I'd imagine the fasteners that may not twist off, if you need to take something apart, may need a good soaking with a penetrate. I got a recipe from this site more than several years back, of a 50/50 mix of ATF, and Acetone. I used about anything sold on the shelf, and used KROIL for years. This 50/50 mix even beat KROIL hands down. Mix it in a dish detergent bottle for a handy applicator, and, so the Acetone won't evaporate. I started off buying a quart of each, just to try it. After that was gone, I started buying it in gallons, so it's always on hand. You just have to try it, to believe it.
The application that sold me, was the apron adjusting eye bolts on an old manure spreader we had here. Extremely flaky, corroded rust from acid in the manure,and just being weathered. I started a few days before starring to work on it, and gave it 2-3 shots a day, every time I walked past it, before I planned to work on it. I hand wire brushed the flaky rust from the threads, and gave it another shot. Once I broke the double nut lock nuts apart, I literally spun the nuts off with my fingers. Sold me right there.
