Apparently the best in terms of power is something that flows straight down...Engine Masters did an air cleaner shootout and the winner was IIRC a salad bowl with a K&N flat filter on top...
Check it:
https://www.youtube.com/watch?v=EkpsydS8JXI
Steve H
SPF 1768
Based on this i have a 9" round (that fits into the hood scoop) with a flow through top: Thinking actually of blocking the sides from the inside...