Progressive or direct??????????
When I was racing my original 63, I drove it on the street and at the track. Ran progressive on the street, and hooked it up straight at the track. Was the thing to do. Don't ask me why. We all did it. I've been racing this car with it progressive. Hold 4-4.5 on the line, nail it and go. I don't know that you could tell any difference with it hooked up direct. When you slap your foot down, they both hit WOT at the same time, hooked up either way. I don't remember ever having to retune for hooking up direct. The carbs are WOT all the way to the end. Same as if hooked progressive. Same amount of fuel through the squirters. I really don't think it makes any difference. Only reason it's crisper direct, is you are moving both carbs at the same time, but less travel to get the same result. Like 1/4 throttle direct compared to 1/2 throttle progressive.
Just my opinion. Been wrong before, might be wrong again. But I don't think so. I think Ronnie is right, except I doubt there would be even .010 difference. Maybe .001 if any at all.
I do think progressive runs cleaner on the street. Cheaper, too. But, then again, it takes a certain amount of gas to get a certain speed. One carb or two shouldn't make any difference if both are jetted the same. Just less travel with 2 hooked together direct.
Like I said. This is my opinion.
Fred