Hi Curl,
I recently spent 4 months in Canada and the U.S.A.attending shows and organising engravers, colour casing etc. Anyway as a result of this trip I currently have around 20 x completely finished barrelled actions, polished to 600 grit ready to be fitted with stocks in the U.S.A. I am heading back to the U.S. in the next couple of weeks to get a U.S workshop established as there is not the skill base in New Zealand for engraving, colour casing etc. Additionally I had some issues with the first prototype rifle wood shrinking quite significantly because the humidity in N.Z is so much higher than say in the Rocky Mountain regions of the U.S.A. So all things considered it makes sense to have the rifles finished in the U.S.A. So to answer your question there is no 11% to be added or Red tape, as the barrelled actions are already in the U.S.A. There will just be the shipping and insurance to your FFL from Wyoming. I currently have 7x57, 270, 30/06, 7mm Rem mag, 300 win mag, maybe a 300H&H, a few 375H&H Belted and a 404 Jeffery in the U.S.A.
If you desire a 375 flanged can do. The actions do reliably extract rimless as well as rimmed cases. The extractor is the same and the "bite" is also the same, and they both work on a rim. There is a rather powerful spring applying side pressure to the extractor. (Strangely enough it seems to work almost as well without in place.)I know all the traditionalists like the rim but it isnt necessary. Its way easier and cheaper to get ammo for a belted, but as I say if you want a flanged no problem.
Open sights arent an issue. I have fitted NECG H&H band front with flip over ivory bead and a standing V in the Quarter rib. They are quite usable too with the standard stock shape. You dont have to mash your face into the comb to get a correct sight picture.

Thanks for your kind words. Chisels and files just cant compete with CNC and hand finishing which I guess is why all the top end makers in the world use CNC today. Additionally my rifles are new and as tight as a Swiss bank vault, lock time like a win M 70 and a fully adjustable trigger with no creep etc.
I used to dream of owning an original but that flame has been well extinguished now.

Cheers

Glenn