Flusher, your two old MM drills look just about like the two old JD drills I use every year to sow.
They've spent their entire 60-odd years outside and get used about one week a year. For a period of that time, maybe 20-30 years ago, they sat unused for many seasons until my dad resurrected them in the early 1980s. Unlike yours, they do have modern conveniences like rubber tires, however.
Every year it's: grease and oil the moving parts, gouge and clean the feeders and chutes, make sure everything still semi-meshes once the gears are engaged, and let 'er rip. They don't fail and probably won't in my lifetime.
Sandusky's old drill is a project but I wouldn't shy away from it all especially assuming, as he mentioned, that he can have it for peanuts.