I'll reflect on whether to leave the Fender decal on the headstock or not. Since it will obviously not be a factory bass, I might leave it and enjoy the patina of the headstock and decal.
It's a real Fender neck, so why not?
Looks good. Let us know if it fits the pocket rout when you get it.
It's the right dimension as far as width at the heel, it won't be too wide for the body, but Tele neck pockets are squared off and the Musicmaster is slightly rounded like a Strat. Plus I think the original Musicmaster/Mustang pockets are a little longer. Not a problem if he uses the unrouted body.
The routed body would need some adjustment at the end of the pocket. It also doesn't have any extension above the body, so there's not as much support for the heel unless. That probably won't be a structural problem.