Glenwood Marine has a good selection a BB Chrysler parts for marine use. Aluminum front cover/mount and rear bell/mount will save weight over the OEM Chrysler Marine stuff. Their aluminum exhaust manifolds and risers will cut about 75 lbs of weight over the OEM iron parts.
It's marine parts, expect to pay. OSCO replacement iron manifolds and risers are ~$750, the Glenwood pieces will be ~$1500.