OC implements. JD Manure spreader, IH Drill

It has 7.50-20 tires on it, and one still holds air after sitting 40 years. The other doesn't. I'll be putting a new tube in it soon. I also need a few links of chain for the apron chain. There is one link that is broken, but I didn't have my chain breaker with me that day and I couldn't get a link off for reference. Would anyone know what size of chain is used on the apron? I hate to buy a whole roll, when I only really need a couple links. One for the repair, and an extra or two. 

I hooked onto the spreader and pulled it around with the beaters engaged, and they work perfectly. I think a little grease and TLC and this thing will be ready for work again! It'll be my luck I'll get a load and chain links will start snapping....

Now the other piece....it's a McCormick Deering grain drill with 12 single disk openers. It is the old type with the tall steel wheels. (It doesn't have a rope trip mechanism, sadly) The shaft that runs under the box that turns the seed out is locked up. (Probably from being kept outside its whole life) I hooked it to the tractor, and raised the levers. The chains that drive the drill both snapped faster than you can blink. I can get the square shaft to turn about 1/4" back and forth, but that's it. I put a wrench on it with a 3' cheater and couldn't get anything to budge, other than move that 1/4". I sprayed WD-40 on all the parts before I left, because that's all I had. Next time I go out I'm going to soak it in the ATF/Acetone mix and let it soak. 

Any other advice on getting it un-stuck? I'm hoping I can plant 5 acres of Milo with it at the end of March. Fingers crossed. 

I'll try to get pics uploaded soon. 

My great-granddad had them, then my great-uncle inherited them. Then he gave them to me several years ago. However, the will says even though the land they are on was deeded to Dad, the aunts can take whatever they want from the land. I'd move everything, but that would stir up a hornets nest, since they've already taken photos of everything. I'm working on getting a copy of great-granddad's will that says the equipment all belongs to my great-uncle. That's my only hope for "written proof". My great-uncle said he would testify in court in my favor, if it came to that. My initials are painted with a stencil in hard to reach, inconspicuous,  places on all the machines (spreader, drills, binder, etc), so that may help?