Which one would you keep and use if it was finished?
Since the JD 70D requires the most work to complete, I'd sell it first.
If you can use the Case and the tires still hold air, or if tire boots (liners) and new tubes will patch up the rear tires, I'd probably finish the Case to use it. Skip repainting it for now.
You can probably sell any of them and buy a similar working unit for less cost than to finish fixing it yourself. It might be worth your time to reassemble without fixing anything that is disassembled, so buyers can see that it is a complete unit. Beyond that sell them as-is.
This is just one guy's opioion, you'll know what's best for your situation.