Bwana,
Welcome to GBO. Home of the handiholics. Yes there was a full mannlicher stock model made a few years back. Don't think they have been made for several years, but the stocks may fit later models. Don't remember the calibers but according to the "K" in your serial number it should have been a 1994 model, if I figured correctly. "U" is 2004, start up the alphabet backwards till you get to your "K". That should tell you the model year. I don't think you can participate in NEF's barrel accessory program, because I think your action is a "low pressure" type. Do some searches on this topic. Nowdays, the low pressure actions are the shotgun and some low pressure centerfire rifles. They are the SB-1 actions. All the other high pressure actions are SB-2, like the 7-08, 06, 308, etc. Can't help you on the other questions.