I'm wrapping up the conversion from 318 to 360 Chrysler and about to drop the new engine in the boat. The 360 has risers but the 318 did not. Just ninety degree elbows off the end of manifolds. That old 1974 Volvo 270 outdrive originally had the flapper on exhaust port but when that blew off and I tried to replace it, I discovered that technology was discontinued in favor of exhaust bellows with flapper in it so that's what I used as replacement. Now I may have some trouble with steering linkage clearance with the 360's risers putting the down exhaust too close to the transom. My questions are these: Were risers meant to replace the flapper in bellows? If I run the 360 with the flapper bellows do I need the risers? If it's a one-or-the-other situation (and I suspect it is), which is better? Thanks.