The #3 and #1 are the same action except for the lock on the lever, lock notch on the lower tang and the lever shape. You can exchange the extractors and the barrels and the wood, including the butt stock if you modify the lever on the #3. If you pull the wood off, it is very obvious that they were originally designed to have a free floated barrel. A fellow used to make a replacement butt stock for the #3 that had the pistol grip moved back so the #3 action could be used as designed, giving a longer more plesant to shoot #3 big bore.
The forearm is glass bedded to the hanger. The barrel channel is cut with a channel cutter to give air space for the barrel itself.
The scope mount rib is removed, the end at the receiver is releaved to give a paper thin space between it and the receiver. When put the scope mount rib back on the barrel the screws are snugged with three fingers only, using blue lock-tight. Do not gorilla tighten the screws.
I have a few #1s, a couple #3s and a #13. The 13 is a modified #3, 22 Hornet with all #1 furniture, barrel, wood, extractor, etc, in 7mm RM. I personally do not care if their 4” warranty is voided on a single shot rife if I can make a #1 or #3 shoot .3 inches at 100, by fixing it myself. If you need to have a warranty, be warned that doing anything to it, including all but looking at it real hard, voids the warranty.
I have been an RCA member since 75 when the RCA was formed, but some things Ruger as a company does are just dumb and a single shot guaranteed to shoot 4” is not dumb, it is silly.
Oh, to set things straight on pieces and parts, Ruger makes receivers (a gun by ATF definition), jobbers make the parts to specifications. It is a common practice in manufacturing to contract various non serial number items out. Example, my first production MRC WSM actions were cast at Ruger, rough finished at S&W and final finished and assembled with the bolt at MRC then shipped to me.