According to the May 1975 Final Edition of the MPC the 1968 390 4/B had three different air cleaner assemblies.
The first was for the ("GT" with 4/B carb.) it is C8OZ-9600-B which is 17.00" dia.- 4.20 high.
The second was (except "GT") (with 4/B carb.) C8OZ-9600-A which is 17.00" dia. -4.20 high. This assembly was the same as the "B" assembly except it had a painted top.
The third was Canada only ("GT" with 4/B carb.) (open emissions)
C7ZZ-9600-F it is 16.79" dia- 3.66" high. This, according to the MPC, is the same assembly for the 1967 390 "GT".
I brought this to Jason's attention shortly after he bought his 390 CS in another thread.
I agree this thread needs to be moved!