I ran a 750 vac secondary on a built 350. Started it up once a month in the winter. Usually when it was 5-10* F out. I'd pump the pedal once then push the pedal down half way and pull the choke out all the way. Crank it, soon as it fired I'd push the choke back in halfway. As it warmed up I'd push the choke in a bit more.
I modified the choke ramp that the high idle screw ran on though. Factory set up I had too much choke (blade closed) and not enough rpm. I ground the cam to a better shape so I could have the choke blade half open but with lots of rpm to keep it from running rich, loading up and quitting.
You don't want to pump that holley too much or it will be a bear to get going.