Velocity stacks will only work if not stuck out in the air flow (inside a hood scoop were air isn't traveling over the top of the stack). The bug catcher top fuel look came from the square trap door fuel injection set up of the late sixties. a better solution is two air cleaners or better yet a home made single air cleaner with one large filter.
Usually the filters are too small in the butterfly scoops. K-n filters help , but the small diameter filters are still a problem . I have a 11x5 K-n filter on my 5" high velocity stack. It works awesome. I don't drive 120+miles an hour though it is a showcar.
Im running a 355 with a 420 Mega Blower in 74 nova and I use 2'' plastic adapters with two 4150s 750cfms and then I made my own trap to seal the dual 6'' air filters even with the 7'' cowl hood, only problem is I get pulled over where ever I go, cops give me grief about my stuff being too tall and obscuring my vision supposedly. WHAT EVER!
When the front tires come off the ground about two foot whats the point? Like I can see anyways, hell im luck to steer!
Maybe thats what theyre pullin me over for? LOL!
I have always like the hood scoops but I have noticed that with butterflys they tend to kill my ETs at the track by 2tenths of a second unless I keep the open from the get go.