As a general rule, marine engines like more carburetion than the street driven engines. As Frank brings up, engine responsiveness may be crisper with a smaller carb on the 256 engine but a 600cfm Holley carb can be tuned to work well at both idle and full throttle.
Holley model 4150/4160 vacuum secondary carbs that appear to be too large in cfm capacity can be very forgiving in that the secondaries will open up only the amount that is demanded of them assuming the secondary diaphragm spring is sized correctly. And unless those springs have been modified after the carburetor has been originally purchased, most of the time they are very close to being right. For this reason, it’s not a problem in oversizing a vacuum secondary carb on a particular application and getting away with it.
Lorena, Texas (South of Waco)