Question about buying Carter BBD for my 318 (unless I should look at something else)

And what's the deal with manifold gaskets (or maybe they're called flange gaskets) that are really thick (like 5/16 with metal sleeve inserts) vs 1/16 ? My current bbd has the thicker gasket, the repop I just bought has a couple of the thin gaskets (with notches) - no idea why they sent 2. The 5/16 gasket with metal insert is correct one. Insert so gasket is not crushed,thickness for heat block, keeps carb cooler, and matches length of choke rod.With thin ones choke rod too long.