When we decided to install a 427 TP engine in Brother Lon's then-new '67 Mustang, a test engine's pieces (from the GT40 program) were made available through contacts at 'Triple E'. We got all the upper half of the engine, to include the heads, complete, the dual-plane manifold, and the pair of 652 center-squirter Holleys. We didn't get the carb linkage and sourced it from 'he who isn't mentioned here'. (hwimh screwed us so that's the reason for my own antipathy toward him.)
That combination was probably as scienced-out as carbs get, since the necessity at LeMans is to go flat-out down the Mulsanne straight and a little further on to creep around Arnage. They say that at Arnage you'd be going at about 15-20 MPH and AJ Foyt has claimed to have hit 240 before lifting on the Mulsanne.
In its later iterations, we tried a whole host of carb sizes on Lon's 427 Mustang. And, ultimately, with the help of the then-new Fuel Injection Group at Holley, we installed and tuned a pair of the then-new 9000-series TBI units. I wrote about the experience in several different magazines including Super Ford and Mustang and Fords.
We did testing on the half-mile track at T&C Livonia using an accelerometer to check on improvements. The end result was to have seamless street manners and to have cut almost two seconds off the track time.
As Jay said, "...you'll never go back."
KS
