The CMP now has a custom shop that can do most of the work for a vintage sniper rifle. If you can find a suitable 1903 donor action they can barrel, stock and install scope bases for the '03 based 1941 USMC sniper setup. You would have to come up with the 8x Unertl scope, or a Leatherwood reproduction, which are almost as expensive as the rifle.
http://www.odcmp.com/Sales/customshop.htmThe quickest and least expensive route is to purchase a Gibbs 1903A4 reproduction and then you wouldn't be butchering an original.
http://www.gibbsrifle.com/1903-a4_sniper_rifle.html