Offenhauser 4006 Carburetor Adapter
$81.00This Offenhauser carb adapter will work on their flathead 4 brl intake manifold (also Y-block Ford and other apps) to put on either a Carter AFB, Edelbrock Performer or Holley std bore 4 brl. ( AFB or Edelbrock won’t work on 48 and earlier engines because of the water outlets).  The manifold base measurement is 3 & 7/8″ X 3 & 3/4″.  It is prox 1/2″ thick.
Holley 4 bl Carb to Carter AFB & Small Rochester 4 bl manifold