Re: Barrel length???
a generic .308 will never use all the barrel a 26" will give you. A 24" yes, but a 22" will be just about as good. I'd go with a #5 contour at 22" long. You'll get a stiffer barrel than the samething in 24" or 26" with less harmonic problems making your groups a little more consistent.
As for barrels, I'd order in one from Sharp Shooter or Pacnor in .308 National Match and be done with it. They are better barrels than the Shaws and some of the others out there.