Exactly,
The smaller sized 'plenum' on the 'Streetmaster 318' is designed for that purpose,
a smaller CFM-rated Carburetor.
The early Carter AFB's {Advertised @ 500 CFMs'} off the 273 Commando have.
* Primary ....... 1 7/16" {1.437"}
* Secondary ... 1 9/16" {1.562"}
A too big Carburetor on the 'Streetmaster 318' defeats the intent {purpose} of the
low-rise single-plane Manifold.
I have used an older Holley 550 CFM {1 9/16" x 1 9/16" Throttle-Bores} with the
'Streetmaster 318', and it works like 'A Charm'.
