So, I just got a reply from Jim Clark as to the Carvers impedance caps.
Just as I suspected both the 4 and 8 ohm taps are wired together. Newer models will only have the one tap.
Here is what he stated.
" 4 and 8 ohm are on the same tap.
There was a transformer update at one time, and the 4 and 8 ohm taps no longer needed to be separate. The binding post were left in place instead on adding covers to the cover the extra holes. Bob buys parts years in advance.
At some point the extra pair of post will be removed and the chassis relabeled 4-8 ohms on the single tap. Functionally 4 and 8 ohm are the same."