The reason your engine quits, is a severe case of lean. A vacuum secondary is only metering fuel (remember no acc pump) to the intake when the engine is putting a lot of vacuum thru the side pod. In fact, many vacuum secondary carbs never open all the way!!
Get one of the Holley quick change housing kit and the spring assortment (# 20-59 and 20-13, less than $30 total). Start with the lightest spring and work your way heaver. You will be able to tell when the engine likes it !!
A rebuild would be insurance and also make sure you have selected the correct power valve.