#1). It is "P" 14. The British called things "pattern of" and abbreviated it "P". US used "model of" and "M", so it is P14/M17 while exactly the same design. Of course the US demanded that theirs be chambered in .30/'06... not .303 British... The .303 bolt face is perfect for belted magnum cases without alteration. .300 H&H, etc.
#2). There is bad press about the ones made by Eddystone at Baldwin Locomotive works (in Eddystone, PA) owned by Remington and part of their contract. If it says Eddystone, you might want to have it magnafluxed by any automotive machine shop to check for cracks in the receiver ring where the barrel screws in. Usually no problem unless the barrel has been removed to rebarrel. But, BE SAFE!. And much cheaper than picking parts out of your face IF YOU LIVE!!!
#3). If the ears have been ground off, where the original rear sight was... Oh boy... ... ... HOW MUCH? [Some had a hole under the rear sight spring. It was filled with weld, usually.] There are bases available, but you will have to do some measuring to see which ones fit. If the original receiver contour was followed, that is easy. Most factories have made bases to fit the design. If the artist decided to go "flat"... good luck. The supply of surplus guns dried up long ago, so you won't find bases at Kmart. Contact factories and you should do o.k. on the first or second try.
#4). Shorteneing the magazine from 6 rounds to 5 rounds to make for a flatter bottomed and sleeker stock was common place. Again, go to the factory and ask for the stock for the shortened magazine rifle. If the person you are talking too knows anything about these... Again, how well was the work done. You may need to do some fitting, but that is like working on these new plastic car bodies... (ha, ha, ha...)
#5). Remington, after the war, used this action of commercial rifles. Model 30/30S and Model 720 if I recall. You can cross check for parts with these model numbers. Might fit. Might need fitting.
Mr. Ackley did not think that these actions were overly strong, but plenty enough strong. (Mine are winchesters) I think Mr. Weatherby developed his first rounds and commercial guns on these actions. They are large and heavy. Lousy for a .223. Knew a 'smith who told me about one just re barreled to .22/250. If you closed the bolt too fast, the cartridge, the SHORT cartridge would jump out of the action over the receiver ring. Problem in the excitement of battle with p'dogs... (ha, ha) .375 h&h, ABOUT RIGHT, with a good recoil pad (or larger...) ... LUCK