Choke thermostat /RAGE

Are you getting a nice stream of pump shot right of idle? may be a clogged shooter.. When you put it in D are you touching the gas or just the act of putting a load on the motor causes the motor to stumble and die? That sounds like a lean condition. put your hand over the air horn at idle..does the idle go up? That is a lean condition. The 1920 has an economizer valve in the bowl. they tend to get plugged up and stop working properly. A good soak and blow out helps. The BBS is supposed to be a superior carb but millions of 1920's were built and worked fine.....also valve adjustment is very important on a 6 for idle and driveablilty, adjust them after they get warm, no need to have them running.