Just a few shaker comments,
The shaker midplates are all the same, except for the holes that mount them to the base. 1970 midplates have the 2V/4V stamping and 2 holes at the front, and slots on the sides instead of holes. Some feel that even the 70 CJ cars got the 2V-4V top, but I know of 3 70CJ cars that have a single hole top that are almost certainly original to the car.
The shaker bases are all unique between year and application, so you really have to do your homework. Some are really rare (69 390) and some are really valuable (Boss 302)
BTW BB, your base shown is a Boss 302, not a 351W
Hope this helps, John