You have to leave(or weld) a 1/2" dam on the plenum floor(on the open side). Mopar used to have instructions on doing the mods. Look around and you might find them. You will also need the carbs setup for the different fuel distribution....jets, metering rods, clusters, linkage, etc.. Mopar used to sell the carb kit, PN2836137.

I ran that setup for many years so if you have any more questions, send me a pm.
Fred