Shaker Base Plate 2×4 Carb

I have a complete shaker assembly. My hemi shaker base plate is set up for 2 holly 600, 4 barrel carbs. I believe it's the marine manifold setup with a 8 5/8" center to center spacing.
I'm looking for the dual 4 barrel carb base plate piece with the 6 11/16" center to center spacing.
Any ideas on where to get it? And quality always counts...
Author: Mike H