Well, i've a big experience In re-barrel process, so it is not a problem to make it "from scratch", or make a some reverse process for it.
The biggest problem in .308 barrel making, is big diameter "ring", between barrel extention and all other length of the barrel.
My friend made a new barrel from .308 blank with dia ~30mm, by using a separated ring, witch was placed on biggest dia, and TIG welded. I plan to do that too. (I have one DIY argone welding chamber, to get a stable welding results).
I have a headspace gauges, so it will be not a problem to get a relaible .308 barrel.
Will left a blueprints here, when i finish it.