While I can't tell you for certain whether or not a factory No. 1 stock will fit your No. 3, I can tell you that I put an aftermarket semi-inletted stock on my No. 3, and I didn't have to bend the lever or alter the shape of the pistolgrip...it just went right on.
I removed the barrel band (it's just cosmetic, the forend screw actually holds the forend on) and reshaped the factory forend to a more pleasing (to me) shape.
You can get most parts for your No. 3 (uses the same internal parts as the No. 1) from Brownells...Ruger won't sell you any parts, even a stock.
Greg