BST,
Those prices are considered fair market by most sporting clays shooters. Since you're already in Montana, let Bob James of Montana Long Guns in Polson do the re-heading work. You should easily be able to get your 1/8" adjustment and nothing should be visible to indicate any work was ever done after the stock left the factory.
If you have any question regarding the exact dimensions you need, it's worth a visit with Bob James and a P.O.I. fitting session. Bob has built some great stocks for world class competition Sporting & FITASC shooters and instructors like Will Fennell from South Carolina.