I don't think I'd use a flat tappet cam in a block that is roller-ready. CompCams will probably have the best price on a roller cam for your application. Call up one of the tech guys and talk with them....The first cam on the list is usually the one to use for a mild application and the first one in this case in the marine, roller cam, carbureted section is the 08-416-8. That is the number for standard rotation. Talk to the tech guy to order reverse rotation.
1-800-999-0853