Riflemanusmc, Shilen makes the .366 barrel blanks.
I have put a few into Mausers in the past. I intend to make one for myself in the near future.
If you need help, contact me at szihn@wyoming.com
I can make about anything you'd like.
If I had your old 30-06 barrel I could copy the shank and headspace dimensions, and it would be a screw-in fit. Any length and any contour you'd like.