A friend brought me a Partial 67 E Shotgun. It's in decent shape, the barrel, tube, receiver and wood. He's missing the bolt assembly and the entire trigger group assembly.

My question is this: Are the series interchangeable? Numrich has a single schematic for the C, D & E.

I have found the parts for a C-series, but not E.

Will they work? What was the difference in the series?

ETA: Appears to me that all of the series from the 30 up to the 67E are interchangeable, then the F series goes to a different trigger guard with a trigger guard safety and a different stock.

There were slight changes. Easiest way is to get the factory parts list.  If the #s are the same, they're probably the same.  If not, you're SOL.  

BTW, a few years back American Gunsmith magazine published my article on the Savage 167 shotgun.  It describes how each part works and interacts with one another.