Very cool and innovative conversion. Lemon heads, jaw breakers, red hots, Mike and Ikes, Hot tamales, little Valentine hearts, and any other box canies should work. Was there a metal piece of flat spring steel in the back to adjust the height of the opening? I haven't taken mine apart in years. I don't believe there is, but I know my Candyette has that kind of adjustment so two products wouldn't get pushed out.
Larry, There is a spring on the back of each column, but the boxes I used are almost too deep so they don't help, if the product was a little shorter they would work perfectly. I did need to remove them, but they pop in and out easily.