On my W-2 I use a 2" adapter but on my W-9 I milled
the 420 intake to take the carb direct on the manifold...
I didnt think I needed more plenum volume with 405ci
plus I didnt want to have to change the air pan on
my scoop if I change engines(thats how much taller
the 420 is over the Indy W-2)