None of the rifles mentioned is a custom one.
Steven Dodd Hughes, a famed stock maker, is a member here. Hit the forum on S&W's made from about 1896-1961. He posts in there. He may see your post and PM you what he charges for stocking alone. I belleve that he works with Tom Burgess and other talented metal workers for the other parts of the rifle.
Famous custom makers have included Griffin & Howe, Dale Goens, and John Warren. Jack O'Connor's rifle maker was Al Biesen. In England, Holland & Holland, James Purdey, John Rigby (now back in business in London), Westley Richards, and W&J Jeffery & Son are among the best known..
I don't think you understand what a true custom rifle is! But the sticker shock is going to make you realize VERY quickly that you probably can't afford one. If lucky, you might find a used one for $10,000. New ones probably begin there and exceed $100,000. Some production companies, like Beretta and Merkel, make very fine guns that are standard models for them, but which are so well made and so ornate that they are almost custom arms, except that I don't believe that they measure the owner for stocking, made to order.
Several years ago, I was in the Beretta Gallery and handled a double .470 that was $45,000. H&H sometimes charge double that for their own doubles.
On the off chance that you are serious about pursuing the matter, begin by getting annual Gun Digests and seeing whose work is featured in their custom pages. And buy copies of the Rifle magazine and respond to ads from the rifle makers and stockers therein. I believe that Weatherby also still accepts custom orders. Oh: Sporting Classics magazine also has articles and ads on custom guns. Study at least two years of issues.
Keep in mind the difference between a true custom rifle and a high grade production item. In the case of the custom arm, the customer specifies the action, the barrel, all other metal work, and chooses the stocker. He chooses the sights, both iron and telescopic, and the 'scope mounts.
If you can't afford to drive a Mercedes or one of the more expensive Jaguar or BMW cars or a Rolls-Royce, you probably shouldn't be thinking of ordering a custom rifle or shotgun. They are not meant for persons of average means. They are luxury items that are also individual works of art.
Keep in mind that they usually don't shoot any better than a top grade factory rifle. Anyone who thinks that better accuracy is the motivating factor in ordering a custom rifle simply hasn't a clue to what they are about. And if you haven't been reading the Custom Guns section in Gun Digest for years, you probably aren't ready for one. Sorry, but I really believe that.
Oh: it takes a year or more, sometimes a LOT longer, to get a custom rifle, especially from the busier makers.