Yep, crazy world with vintage guitars these days. A good pre-CBS Jaguar still seems undervalued compared to strats and teles of the same years.
If I cracked it open and liked what I saw under the hood, i.e. almost all matching original parts, and I had money to blow, I might drop a grand on it. Then I would send it to a well reputed restorer for a refinish, sell the neck, and buy a period correct one for it.
Does it include the original case?
The "gap" is nothing but a poorly applied neck shim; it's the least of your worries with that thing.
I can tell you that the bridge is definitely not original. It's a Mustang bridge.
The headstock should stay as is. I think things like that give an instrument a sense of history and experimentation (which is all relative, of course).
But the important thing is how you describe playing it. Maybe it fits like a glove, in some sense. You've got the hard facts from others, but there's the emotional factor.
When I was teaching, I would be looking for signs of an emotional connection, bang, bammo. I could walk away knowing that they will want to work on their stuff.
Guitar Center has a Classic Vibe Jag on sale for $399 right now. It probably doesn't sound as good, but I'm sure you could get your favorite tech to get it to play just as well for less than $200. Just saying.