bkarasek, SC is short for Super Cambo. The SC was made in four sizes: 2x3, SC1; 4x5, SC2; 5x7, SC3; 8x10, SC4. 4x5 SC = SC II. Clear?
The Super Cambo underwent continuous development; components, e.g., knobs, and the materials they were made from changed over time. The SCN is an economy version of a late SC2. Shorter rail, reversible instead of rotating back. I'm not sure whether the N's reversible back is Graflok or a bail (spring back that opens very wide) back.
Most components are interchangeable across vintages of SC, some across sizes. For example, SC2, SC3, and SC4 all use the same front standard and boards. The SC1 is the big exception, has its own standard, bellows, boards, and backs but uses the normal SC rail clamp and rail. I said standard because the SC1's front and rear standards are identical. So are the SC2's, but they're larger than the SC1's.
About component interchangability: I use a mutilated SC2 standard on my SC1 as a crutch to support long lenses. I use a 2x3 SF bag bellows; it fits the SC1 standards and is much nicer than the old SC1 bag bellows that came with my camera.