Oh, you'll get it back together alright, and when you do it'll have some real charachter. I've been a member here for 8 or so years and I've found out everything I've ever needed to know here. Just search thoroughly and do lots of reading before asking questions, as many of them have been asked before and answered quite well.
I have a K3 with a mfg date of 10/72 The best way to tell a K2 from a K3 is that K2's and earlier have a single fuse under the left side cover, later bikes have 3 fuses there. There are ither ways, but when you're in a junkyard.....it's an easy way to tell without looking too closely.
Anyway, the majority of parts will fit the majority of frames side covers, airboxes, seats, fuel tanks, and a few other parts did change over the years and either won't fit well, or will fi with some easy mods. many of these parts from 77-78 are different...but may fit with a little effort. (examples are fuel petcock on different side, seat hinges on different side, side cover designs varied over the years, I dunno if the fit is all interchangeable) You don't have to do a perfect restoration to have a great bike, some do but they don't all see much street time... Some of the coolest bikes I've seen are more hot rod than restored or cafe racer.
Be sure to hook up with the locals at
http://www.nehondaguys.info/ there's a pretty good bunch of guys in the Boston area, lots of parts and lots of know-how too. Welcome, see you around!
-Alan