I drilled holes in our 272 with the biggest hole saw that would fit in the trim ring . Ours had 383's 425 hp in it sounded great 69.8 on GPS.:D

i can see the small piece maybe .25 inch plywood from the rectangle exh hole is there another baffle behind that one. is there 2 in each box or 1 . i think i will just drill it out not knock them completely out. so if theres 2 should i do both