This is an awful thread, nothing but dismal hopes and shots in the dark. Shoulda bought the kart first and foremost {yeah, yeah I know you're trying}, no matter how long it takes to get it and
then report here with questions. This is a "putting the cart {haha} before the horse" type of fallacy.
Sorry to mention this, but $100 dollars isn't a whole lot of money these days. It's a respectable amount, yes, but it is nothing extravagant for a bare frame, four wheels and tires, a seat, some linkages and a frame not covered head to toe in rust {like most seem to be}. Trying to identify it as a rare collectible go kart worth megabucks is rather secondary to the aspect of "do you like it?"
Come on maaan, get a "surrogate" buyer and nab that old heap. They're obviously not going to sell it to you.
Your photos are craptacular too; mostly ground, bricks and clutter... then you want us to try and ID the thing.
I'm not being mean either, I'm just busting your balls.