A lot of Smiths like to specalize their work, that way they don't have to change their equipment/tooling up. This allows them to put out more work with less effort, and a really good GS usually has more work than time. So it isn't hard to understand why they choose to work with what is most popular.
Kevin Weaver of
Weaver Rifles built my M70 Stainless Stainless Classic .338-06. If you don't mind working with a guy who isn't local to you, he's a great guy to deal with. He always has a lot on his plate, but he'll work on pretty much any rifle. Talk to him and round up all your parts beforehand. Ship everything when he's ready for it, and his turnaround time is usually very quick.
BTW what are you planning for your build?