All I can say is do it for the kid
I would have been the happiest 16 year old to get something like that with a chevy v8 in it. No idea what kinda work you are looking at or the availability of the parts. But if you have the cash and know how that would be something your son would NEVER forget.
Plus those things can be damn nice looking when they are finished and there are not many of them still kicking around.
Just be realistic, once you have seen it decide on if it might not be better to find a newer yj to build for him.
Forget everything i just said and get the Jeepster....man that would be cool