67 slant with 1920 holley dies when engine heats up and choke opens.

Hello,I have the above problem.Engine runs perfect until choke opens.I have replaced the fuel pump,and fuel filter.Engine is perfectly tuned,new points plugs,valve lash,timing adjusted.I have not found any vacuum leaks.I am not knowledgable about carbs.My next step,unless somebody has other tips,will be to install a refurbished carb I have had in storage for a couple of years,just for this scenario.It is a direct replacement,outside of one extra threaded hole intake near the needle adjustment.I just plugged it up with a bolt.Any suggestions would be greatly appreciated. Thanks,Rich