I've mixed different year transmissions/valve bodies several times and not had a problem, sometimes just to match the NSS to the car it's going in. There are some casting differences between older and newer cases, and there have been internal changes in VBs over the years, but I used a 1980 valve body (because it already had a TF2 kit in it) in a 1967 727 and it worked just fine. I've still got the '67 VB in a box sitting on the shelf.