I understand this. My suggestion was that since you like to shoot with a scope, then go with the RPK which I know is already built. I also know about the Century Yugo underfolders, BUT since you CANNOT buy both of these, then buy the RPK and get a kit JUST IN CASE you cannot find an already built Yugo M70 underfolder. In this case you can always have one built if you really want this rifle, and if you can get the rifle already built, then you can sell your kit and perhaps make a couple of $$$ in the process. This way you are not completely out of luck if the rifles dry-up.
About the kits, I have two and the barrels are nice if not too shiny(i.e. NO PITTING). No, I did not get them from CFS and there are many other vendors who sell these.
I also know funding allows only for one rifle but the kits are cheap ($100 and change +/-). If even this is NOT possible then just get the RPK