Fender neck replacement for Squire?...

Not the J version, but I replaced the neck of an older Squier P with a MIM Fender neck about a year ago. It was less expensive than fixing the problems with the original neck.
It works perfectly. Feels good. Frets were level out of the box.
All I had to do was bolt it on, transfer the hardware and fine tune the nut slots.

 

Is the squire so young that he'd be more comfortable with a short scale? Or is he simply demanding a new neck?

 

I'd say 'probably', in terms of it being a direct replacement. As always, sometimes Squier to Fender (or other aftermarket parts) may require a bit of work to accomplish this, basically as Squiers, just like Fenders, are made in several different places, and can tend to gain or lose a fraction of an inch here or there.

Here's a link to those necks (and other GenFender parts) . . . .

Necks | Fender Parts

 

I've done a lot of neck swapping between all kinds of Squiers and Fenders and never had an issue. Sometimes alignment over the pole pieces isn't perfect but nothing has ever not fit for me.

 

The Jazz necks swap out just fine as well.

 

There are a few anomalies out there. Different numbers of frets, slightly different heel shapes, etc. But 95% of them just bolt right on no problem.

 

Then there are three bolt or five bolts to worry about. But generally speaking if we're talking standard 20 fret, four bolt necks, you're good to go.

 

be careful of parts from china, just bought a p/j bass body squire affinity off egay, and the neck heel size is 1/16" to small, for a standard 2.5" fender neck and wont fit without routing. Not that it wont work, but it will overhang a little...it's 2-3/8", maybe from a shortscale bass?, but it wasnt listed as such...get all your measurements, not all are created equal