Actually Johnny, I believe 1411's have the pump arm in the top hole. Could be wrong. I have had some cars that like the top hole and some like the center hole.
Steve,looked it up,you are correct.Top hole.This will explain the stumble off idle. As you know,going to the center hole will give the carb a bigger shot of fuel,and going to the last hole (towards carb) even bigger yet.
Another note here. The 1411 750 (electric choke) carb is set-up different than the 1407 750 (manual choke) carb. It is set-up with more economy in mind,(smaller main jet/metering rod).If it was my carb I would set it up to the 1407 specs. Simple main jet/rod change.