Were i to do this build, i would use the large shank for really no other reason than "just because".
Lazzeroni did testing with the Savage large shank. They intentionally over pressured it to see what one would take. At 120,000 psi they got the receiver to permenantly deform.
Check out Grices. I don't remember a time when there that i have NOT seen a used 270 WSM on the rack.
Incidentally, going by Hodgdon, the 270 WSM with 130gr bullet is about 300 fps faster than 270 Win, and 100 fps slower than 270 Weatherby.
Myself, i use E.R. Shaw barrels. They are made in PA (just south of Pittsburgh). I have had excellent accuracy wiith mine (note, hunting rifles). Are inexpensive. You just missed end of year sale of 15% off entire order.
I have 2 now, and getting money saved up to order 2 more for different builds.