AFAIK there is no good math for plenum volume, runner CC vs. carburetor CFM, too many variables like vertical distance from throttles to floor, CR, overlap.
The area in the plenum floor adjacent to the 5 & 7 ports has a longer and stronger vacuum pull than next to the 1, 2, 7 & 8 end cylinders.

Jenkins explained development of TR SBC 45 years ago.
1. make the plenum larger until power on a dyno stops increasing
2. this will have bad response in the car and bad mixture curve
3. reduce plenum 10%