Some quick thoughts late at night. First you are smart to be concerned with compression ratio. I would avoid increasing the ratio very much in these days of high fuel prices,especially marina gas. YOu don't want to get in a situation where you are requiring high test/octone gas to keep your engine in one piece. The ultimate goal for me anyway, is to set the engine up to run on mid grade gas which is usually a 8.5 to 1 compression ratio with a carbureted engine. You can get away with a little more depending on the cam grind but not much more. Maybe 8.8 to 1. Running 9 to 1 comp ratio is treading on thin ice with no electronic timing controls to retard timimg.
More valve opening duration and overlap in the cam will effectively kill some of the cylinder pressure at lower RPM's but that can be a complicated subject in itself. Be very careful with the cam selection, you don't want to get to radical with a marine cam. Increasing the cylinder bore .030 over raises compression ratio a little in itself,surfacing the block and/or the head mating surface a little more, and the thickness of the head gaskets are a another factor. I don't think the 2.02 intake valves are going to be much of a benefit at the below 4500 rpm range this engine will be running in. If the stock heads are running 2.02 intakes those are Corvette or SS heads, that found there way onto some marine apps., not really necessary on a smaller engine/heavy boat combination.
Bottom line: The piston manufacturer usually can tell you what the compression ratio will be for a certain piston and head combination. Let them advise you. I am guessing the flat tops will raise CR too much though, because the 327's are 1960's vintage and the head chamber volumes are small compared to the later so called smog heads with the larger chamber volumes.
Your 23'is a fairly heavy load for the little 327 to push around so don't kill it by running to much cylinder pressure.
It is already going to be working hard enough. Prop choice is critical to letting the engine breathe.