on the 500hp's who made the intakes for merc and did they all have the brass inserts?

I think I remember reading somewhere that they are Dart intakes.

they are darts .merc grinds the name off .you can see it on the left side -also no brass lining

If i remember correctly i think all of Merc's HP series motors are Dart Intakes. I know my 540's are.

Dart's and I thought they did have the bronze liners. Dart does make the same manifold with the brass so I don't get why Merc' wouldn't use them??