Hello. I just picked up a M1 single plane and don't understand why you are using "adaptors" or modifying the shape when it's drill for a Holley carb anyway?
The smoother the transition is from the carb venturi to the plenum, the better the better the airflow will be. Welding with contouring and adapters in this case can minimize the "ledges" the airlow has to go past. Airflow gets turbulent around sharp corners.
