A street vehicle air cleaner is not required on a boat - no dust on the water. At least not yet. So just a flame arrestor is all that is needed, mostly to keep the bottle caps out of the intake.
When I had mine, 79 350vette with VP IO, it had some funky distributor on it. Normal GM distributors were not marine approved - DUH. Since marine parts are 4x as expensive as car parts we spent about a hours matching up the point, cond and cap to car numbers. Same $hit diff number and price. One thing that is a real good idea on a boat is a fuel filter.