^^^ I am using a tall Weber style rectangular open element filter. It has plenty of flow capacity.

Screwing with small block Chevys/Fords/Mopars over the years, I've found that open plenum intakes are better in the higher RPM range, where a split plenum is better for lower to mid range performance.
This usually doesn't apply to 4 bangers since the intake pulses are completely different.
Since the Weber 38/38 has sequential opening venturis, it may work better with an open plenum (?)

I have several Weber side draft carbs, 40s and 45s... There is a guy who sells the intake flange for these engines. It would be pretty easy to fab a dual Weber side draft intake. I have access to a TIG that will weld aluminum.
We'll see.
My job changes so rapidly, that I don't have much time to do custom projects like that.
Most of the time I work in parking lots and rent storage space on the road.