It's likely you will be more happy with the oval port heads, particularly with the heavier boat, assuming you will be set up to run in the low 5000 RPM range or so.  You aren't planning on racing it, are you?  The intended RPM range and compression will have some effect on what type of heads you want to run.  The material of the heads is not nearly as important to performance.  Aluminum gets used for racing since it's lighter, but it's also more easily repaired if something breaks, and it also transfers heat better if you are trying to run the engine "on the edge" for racing too.

No real racing. Just fun with my buddies. Ran it all weekend on 7cyls due to a dead cyl on # 3. Hoping it's just a bad valve. But did make it around all weekend. plan was to start on the 496 build then just drop it in. Barely made it to the river.pump got done days before. And with work didn't have time to run it.so much for my rebuilt motor.... oh well it's just money I'll make more.....

Pulled heads on 454 today only to find head is wasted. 2 bad valve seats.one completely unattached one about to go and a nice crack across the valves on another cylinder.
Going alum on the 496. Which ones? builder says Vic jr.are a solid deal.