Remington 700's and 40X's actions all come down the same assembly line. The only thing that separates them is the quality, 40X's having tighter tolerance. 700 actions keep going down the line, 40X actions go to the custom shop.
Although Remington Custom Shop takes a little more care fitting the barrel and stock, you are getting what Remington wants to give you. For example you can not get Remington Custom Shop to fit a custom barrel like a Kreiger or Broughton, you get a Remington barrel. Not saying these are poor quality barrels, just that you get the profile, twist and caliber they offer. Length of pull, barrel length etc is what Remington decides.
If you bought a 700 action and had a gunsmith fit a custom barrel and stock to what you want, it wouldn't cost much more the what you would pay for something out of the custom shop. There is also a good chance you would get it quicker and to your specs.
I have a 40X that started out as a Rangemaster with a walnut stock and Remington barrel. The stock was not the most comfortable to shoot so when I had it rebarreled with an Obermeyer I also had it restocked into a McMillan prone stock. It has since been rebarreled again with a Kreiger.