There are two lengths of carbine stock. The 30" one on all original M1896 and M1898s, and the 32", used for M1899s and as late restocks on M1896s and M1898s (which model is itself a HUGE can of worms).

Yes, all rifle stocks are considerably longer. A 32" carbine stock can be faked from a rifle (especially now with the the more relaxed attitude towards added sling swivels on the part of some individuals - which I do NOT share) while the 30" style cannot, because of the shorter grasping grooves.

There are some pictures and descriptions of fake 96C sights on this website, under "Photos". 1896 Carbine sights are graduated to 2000 yds., and the slide is different in that the area at the notch is about 1/64" lower than the line of the top of the bar at the sides.