I have a 6.8SPC barrel from Rem factory heavy barrel on my 270WSM. You would have to open your bolt face or get a WSM bolt from PTG for yours though. Also consider that your smith won't be able to true the face of the lug surface in the action more than likely, my smith uses a cutter from the barrel end and to use it the recievers threads have to be opened up, then you would not be able to use the factory barrel threads since he would need to oversize the action threads and the factory barrel threads would be too small.
This is what I found....unless someone can correct me?
My rifle shoots great out to 1000+ even without the reciever lug surface trued.
Not sure how far you'd like to take it. There is a wildcat(s) that would work great with your bolt and barrel twist. It's based on the .30 Remington which uses the same rim diameter as the 6.8 SPC and other cartridges like the .224 Wby. Mag, .25 Rem, .32 Rem.... a wildcat that I made off it was the .22 GTO
At any rate all it would take is reamer, case forming die and reloading die set; then you'd have a .270/30 Rem wildcat that might be a lot of fun. Of course you'd pick the shoulder and develop the load.. I'd think just necking to .270 cal from .30 cal would be the trick.
I'm thinking it should give you somewhere around 55grs to 59grs of water volume in the case to work with, maybe a little more. Might be a hoot with the light to medium weight .270 cal bullets.
Just my .02