Lazlo at Ducan's Gunworks (in San Marcos) does work on FN's/Mauser CF/Winchester Model70 Pre-'64 rifles. Might give him a call. Ask specifically for Lazlo (he contracts out to Duncan's IIRC, and handles their more detailed/complicated jobs). I've seen Lazlo's work; amazing stuff (very detail oriented).
The guys at Precision Arms (in Escondido) may have someone as well, but I've never seen their work (and from discussions, it seemed like they handled the more mundane stuff; i.e. bedding, recoil pads). Again, I've never used them, but have heard from some folks that were pleased with work done by their (PA's) contracted gunsmith.
Shoot me a PM for details if you want...