Small Block Cast Iron Intake Part Missing

Hi Folks,

Just built 68 318 block .030 over w/ 675 heads, RV cam and 2 bbl cast iron intake from claimed 72 318 for use in 80 D150 followed by 4 speed 727 auto w/ lockup torque converter and 2.76 gear to use as tow vehicle for kid's Hellcat. [have had some days off here recently] Problem is, after hot tank and crack check on this ebay intake, I notice the (what I thought was manual choke sink) is open to exhaust crossover port. Question: Is there a bathtub style part that would block off this port and still allow for the manual choke to bolt in? Seems like I recall from pulling wrenches in the 70's there was just such a part, but I can't find any evidence on the net.
Thanks for any help! Great site by the way!!