Recoil Bob,
Your gun is a 1903 gun, "0" grade, which was the predessor of the Ideal grade beginning in 1913. Most "0" grades were Damascus barreled, and your gun is choked F/F and has 2-3/4" chambers.
A replacement buttplate can be obtained from vintagegungrips.com, but the forend will be an issue. Do you need just the wood or the iron as well? Without seeing the barrel lug it's unlikely that the one you described will fit, as your gun is a "R" frame gun, as opposed to a FW frame. Your best bet is to find a complete pre-13 set for a 12 ga "R" frame gun that someone is parting out.
The toplever should be straight, and use extreme care if you choose to correct it. Have a gunsmith knowledgeable about Damascus barrels pass judgement, and use only low pressure shells (-8000 PSI).
