Due to the rb25 running coolant into the plenum would these make much difference on these engines? If we could block off those ports then I could see it working but is there an internal path for the coolant if we did? Do they seal without the need for any

It would, as the temperature of the water is less than the cylinder head. In saying this though, even if there were made out of aluminum, there would still be gains to be had. You wouldn't be able to block those ports off I would imagine, given it would stuff up coolant flow to the cylinder head. Redirecting the water ports external of the head would be ideal though. No, they do require glue to seal.