The biggest restriction is the distance between top of the carburetor and the lid of the air cleaner… the more distance the better the airflow! Straight down would be perfect!
I do like to have the spacer between the intake manifold and the carburetor because it insulates some of the heat… but there is a price to pay… I am thinking how to get the most space between the carb and the top of the air cleaner on my new engine built… ! Maybe milling the top of the intake down and then putting the spacer/insulator on top without increasing the height…
wheels are still turning 🤪
you may already saw this: