Agree with most of the comments. Not sure how it would be easier to tune as all the duplex carbs I've seen have fixed load jets with that single screw at the bottom that has very little impact on mixture. My experience with taking a 2 barrel carb, and modifying the manifold to adapt it to a single barrel Head was that it worked ok at wide open but will lose all bottom end unless the motor is really big.
The 50 head has 10 head studs, the B has 9 and not in the same location. You can put a 50 block into a B with a little work.
What goals are you trying to accomplish?