Thousands and thousands of military surplus rifles have been sporterized over the years, to include new barrels in about any caliber compatible with the action.
It is now thought to be Desecration of a Historical Artifact and Devaluation of a Valuable Collector's Item, but when I paid $39.50 for my Mk I in Newberry's Five and Dime about 1962, it was a sensible thing to do (Although I didn't, GI was good enough for me.)
I would expect a Springfield with a .270 barrel to have been restocked and fitted with scope or receiver sight. Can you post pictures?
Dollar value will be only a few hundred unless you can prove it was built by a nationally known gunsmith or presented at some official function.