Yes, Zenith would be the ultimate best option but the correct one you need is hard to find.

Another option I forgot to mention is the Carter WA1 710S (M/T) and 764S (M/T) which were made for the 1949-50 Oldsmobile flathead 6 257.
I plan to test this one myself. The negative is that it has a automatic choke.

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."