I have a No. 3 in .30-40 Krag that I bought new in 1979. It is a very nice little carbine. It still looks new and I have left it original with the addition of a Weaver K2.5 scope in Redfield mounts that were made special for the No. 3 at that point in time. I thought of fitting it with a No. 1 stock and forearm at one time, but I'm glad that I didn't now.
The No. 1 stock will fit, but the lever tip will be very close to the pistol grip.
For sights check with Marbles or Lyman.
http://www.marblearms.comhttp://www.lymanproducts.com/lyman/sights/Not sure about peep sights that will fit the rear scope mount holes, but I sure someone will know.
P.S. I saw a No.3 in .375 Win. at a gun show a couple of months ago. Wish now that I had bought it, as they seem to be scarce.