My '77 318 Volare` had the same arrangement. I removed the entire assembly, cut the flange off the exhaust manifold side of the assembly, welded a disc in the flange tubing hole to make a plug, and reinstalled it on the exhaust manifold. Drove it that way for nearly 100,000 miles before I sold the car. I did something with the air cleaner end too but I can't remember what.