Re: seized up
Bummer. That gouge in the cylinder wall will be hard to hone out. I think I'd be inclined to go for a new engine. Looks like all you really need are the cylinder and piston, if you can find 'em cheap enough. Sorry for the bad luck.
I'm new to Chinese bike engines, so I just bought one and bolted it up. So far, so good. After reading all the good info here, if I build another, I'll tear it down and inspect/check, install 'real' headbolts and such. Right out of the box. Good news? It's not like popping a rod in the in your fresh 383 overhaul. $$$$$$$$$$$! Nowadays, I like and can afford Chinese bikes much better!
Good luck Evan!