Pop the pump arm off (punch out the roll pin that the arm rides on), disconnect the linkage from the choke to the choke flap on the airhorn, unscrew the screws on top of the air horn and the secondary metering rod hanger. Remove secondary metering rod hanger. If the choke pull off is attached to the air horn, no need to remove it. If it's attached to the main body, disconnect the pull-off vacuum from the airhorn.
You should be able to sneak the accelerator pump out now.
Occasionally the power piston will pop out of its bore. If this happens you'll need to remove the gasket (observe how you have to lift the gasket over the arms of the power piston) and then line the rods up in the jets and press the retainer of the power piston back into the bore.
Good luck!