Well, Good news, bad news....
Went back to the guy today with cash. He felt bad about it, but he decided not to sell it. Turns out he's got two of them. He's an old faller and has used square grinders exclusively for the last forty years. Nice guy. I told him that I didn't blame him, and we exchanged numbers and I promised to hound him about it.
Honestly I'm not that bummed about it...I could've taken the grinder and made some money off of it, but now he's going to bird-dog for me for old saws and parts, and he promised to sell it to me if changes his mind, and the guy offered to give me a lesson on square grind any time i wanted. I'll take that any day....