Not even the manufacturers can decide on plenum shape.
Earlier this year I built a 440. The owner had a collection of intakes: T1, T2, Victor, M1 4500. Out of curiosity, we measured the width, ht, & depth to get an idea of the plenum volume. Here are the numbers in the above order: 535cc, 1260cc, 885cc, 1332cc.
You would expect a 7000+rpm intake like the Victor to have a large plenum; however it is 2/3 the volume of the lower rpm T2. Another thing to notice is the T2 plenum is more than twice the volume of the T1, yet both are 2500-6500 rpm intakes.
It would seem the thinking at Edel went backwards & forwards over the years on plenum vol.