If you do an online search for “air filter test” there is a lot of very good information.
If you look at the flow data, WIX HP filters flow 98+% of K&N and have a much smoother flow post filter plus excellent filtering, for a fraction of the price!

IMHO, in my younger days when we were playing with those series of engines, we would build an air ram type intake into the air cleaner- using a couple of 3" diameter hoses.

For calculating the minimumsize air filter, here is the formula:

Minimum Air Filter
Surface Area
A= (CID) (RPM) divided by 25,500
H= A + .75 divided by (D) (3.14)

Key: A= Filtering Area D= Estimated Height H= Height
Note: For Off Road Use Multiply Height 1.5 to 2