Re: What would you spend on this motor
Well, the aftermarket head, spring chain tensioner and machined intake are probably worth more than $85 combined, so yes, I think you got a good deal. The bottom end of that motor should be replaced, however. Or at least the casing. But even if you strip the motor for parts, the aftermarket parts cost more than you paid.
As for the original owner...I don't think it's his age that makes the motor dangerous to him. It's that he thought he could fix it with JB weld. So congratulations on saving the old fellow's life!