It is not the displacement of 216 that makes life with a 4-barrel interesting; rather the lack of oiling, and the maximum useable RPM.
4-barrel carbs have been factory supplied on smaller displacement engines; and have worked quite successfully.
But the 216 was rated for 3300 RPM. Even a full pressure 235 was rated at a maximum RPM of 4200.
The GM 215 CID aluminum V-8 had a 4-barrel option. So did the Pontiac 195 CID 4-banger, and even the Chrysler 170 CID six!
As far as the 195 Pontiac, 2 different 4-barrel sizes were offered: 400 CFM and 625 CFM!!!
But there are a number of individuals that frequent these forums that would love to have that "crappy 1 barrel zenith". Zenith made some of the finest single barrel carbs ever built anywhere in the world regardless of price!
And one suggestion:
Do the headers and the split exhaust.
Then, BEFORE changing to a different carburetor, do an electrical tune-up, and with a friends help do 3 clocked 0-50 MPH runs. Write the times down, and do an average. Now once you have installed whatever carburetor you decide on, do 3 more timed runs, and compare the average to the present "crappy zenith 1 barrel". The results may surprise you. You might just find a two barrel to be SLOWER!
I personally owned one of the Pontiac 195's with the 625 CFM that I subsequently replaced with one of the 400 CFM units. 0 - 60 times were about 2 seconds QUICKER with the smaller carb!
Jon.