Just to clear up a misconception by some posters above.....a Kimber bolt action CRF (controlled round feed) can be single loaded by dropping a shell into the chamber and closing the bolt over it, as the extractor will snap over the rim, just like a push feed such as a Remington M700 or M7.  A M70 Winchester CRF can also be closed over a cartridge without feeding it from the magazine.  
As per the custom versus the Kimber, I'd go Kimber if you like the Montana/Mt Ascent stocks, as it makes the purchase a no-brainer for value.  Or build off a used Kimber MT if you want a custom rifle.....the basic action, trigger and stock are excellent in my experience. Past complaints being about the barrels and accuracy and weak firing pin springs are easily corrected by your smith in the build process if you go this route.