this is what i did on my 440 . Was just a quick made stuffer to reduce intake volume , removed about 20% . Might have helped to have used a "cross" shape and fill area between front and rear runners as well , like where you have carboard . Helped a bit but as i have said before , i feel these are more friendly with bigger cubes and or higher RPM . I was only shifting @ 6000 trapping @ 61/6200 . Felt great on street , ran similar or hair more MPH but was lazy sixty footbraking . I spent quite a few pulls on a chassis dyno with it . Tried different spacers etc .

Tex