Expectations for Neck Swap

Most of the AllParts necks I've owned (and I've owned several) bolted right up to a body that had previously had a neck in it. Usually played well too without fretwork...though I'm sure they would have been better with a crown and polish. I didn't have obvious high frets or sharp ends on any of mine though.

Any tele body that hasn't had a neck in it before will likely need some pocket sanding. This is done on purpose, as it's better to have a tight neck pocket than a loose one and it's easier to take away material than to add it back.

I've heard their are fitment issues with Chinese bodies (like Squier) with American and Mexican necks. No experience directly, but I've seen several people post about it.

 

I'd say a drop-in with the possibility of some minor imperfections - same as with any other-market parts, or even any other Fender parts for that matter.

But I don't think anything would be seriously out of whack.

 

Recently did something similar.
I have a Fender Road Worn body, but needed a slimmer neck and a larger radius (Road Worn neck has a U shape + 7.25 radius.

The Allparts TMVF-C was my best case scenario (Modern C shape, matches the original neck color, and has a 10" radius).

The Allparts neck was NOT a drop in for my body. Definitely needed a little bit of sanding.
As others will mention when it comes to sanding the neck VS neck pocket on the body, sand whatever is least expensive or of lesser value to you.

In my case, I sanded the Allparts neck little by little (from each side) until it was a nice snug fit (not too tight and not too loose).
*Note: THIS WILL REMOVE THE FINISH. But since it's not seen it didn't matter to me. If you were to get an unfinished neck, then make sure you do fitment before you color/finish it.

Reamed the tuner holes a bit (to fit 8mm vintage style tuners)

Drilled my neck holes and bolted it up. Added a TUSQ XL nut and checked my E strings, and I was good to go.

Frets needed some leveling, followed by a crowning.

Looks and feels great! Ordered a second one (Nitro finish) on the way.

 

Without addressing the particular scenarios of Allparts/Fender/Squire, etc. I have had to sand the sides of neck pockets to get enough side-to-side play to adjust the neck for the high and low string spacing, and have had to add shims. No big deal if you are careful.

Hole alignments might be an issue if you get a neck that already has them drilled. Plug and redrill. Also not very difficult to do.

 

matching a Fender body to an Allparts neck. I did one for a buddy years ago and the neck was way too wide. I think it was an oddball though and many people have no issue. I had to "sculpt" the neck.
matching an Allparts body to a Fender neck I dont know.
matching a Fender neck to a Fender body Always good. The most trouble free swaps for me have been MIM Fender necks.
matching a Fender neck to a Squier body I have done this successfully with no issue. But watch out for any Vintage Modified model guitars. Some are odd.
Neck pocket sanding? I never try this, paints chip very easily around the pocket.

All in all, the MIM Fender necks are the best IMHO. And at $200-225 finished and ready to use you can't beat them. I have had a dozen other aftermarket necks; Warmoth, USACG, MusiKraft, and more.

Neck fit in the pocket is an aesthetic thing, no other value. Even if you could get it within .001" that would introduce the possibility of vibrate at the interface and buzzing. Which they dont ...but just saying. If intimate contact was a "thing" no one would buy Fender guitars and only Gibsons. JMHE

 

Out of your four scenarios, the only one I don't have any experience with is the last one - Fender to Squirer.

AllParts and Fender are interchangeable in every experience I've had.

AllParts is licensed by Fender to produce after market stuff; my best guess is that to be licensed requires providing parts that will interchange with a certain degree of accuracy.

 

I have never had that problem but probably because I am very careful.

 

I personally don't alter original Fender bodies to accept aftermarket necks; I don't think there is any advantage in doing that.

It is definitely possible to improve an already good Fender guitar by using an aftermarket or custom built neck. It all depends on what the owner wants or requires from their guitar and the quality of the aftermarket neck .