I read it for decades and remember the era you speak of. This is where the mil. surplus advertisers advertise. Siam 98's were common and "no ffl" back then because ammo was not considered available. BUT RCBS came out with form dies to make cases, so no more. Could you be happy with an 8mm on the .45/70 case (I think). Ask at RCBS or ch4d.com or Redding... Case form dies.
I think Shaw was a supplier of barrels. I had mine installed by a local 'smith. I shot a 4-5 inch group with 300 grain Hornady's at 100 yd off bench, IRON SITES, which is pretty good for me. I am happy. (He used Wm's "Guide sites"...) ONCE I loaded some 500 grain lead bullets to hot trap door levels. THEY KICK. B). The bolt will handle the .50/70 gov rim (which is same as .348 WCF)... so if you are inclined to "self abuse." I used some 93 Mauser parts for replacement??? Mr. Ackley, in his books, wrote about a series of cartridges made on the .348 case, down to 30. .450 Alaskan was the "big thumper" for the mdl 71 Win lever action and big bears. 40 & 41 cal too. Now I am happy harassing p'dogs with much smaller bullets, your bucks, your call, enjoy... happy trails.