There were no pipes ........................
that went with that exhaust system. There was a cast aluminum cover that had raised fins on it like on an air cooled cylinder. For closed up quiet lake running where you had noise problems you ran with the cover on which was secured with two screws and the exhaust went down the tower housing as was intended. The place where the screws went is obvious.
When you wanted to wake everyone up or go to a race where noise was OK, you took it off by removing the two screws. The piece was made by Quincy as someone already stated, but to my knowledge it never came with pipes or had any type filler block with it that would allow pipes.
Gene East is the Quincy expert on this site and I am sure he will chime in.
ADD: Lots of guys used to have the waffle pattern of that cover burned into their upper biceps on the outside of the arm from letting their arm be where it should not be when carrying the boat out of the water.