look to the aftermarkets if you cant find oem parts. places like dennis kirk, shadetree, etc will have kits specific to that carb. the downside is half the diaphrams dont seem to fit correctly. the ones i have used i have been lucky and the important parts fit. seems like about half get tossed.
when you open up the pump portion of the carb pay close attention to the orientation of the diaphrams and gaskets. mark them, take pics, whatever you need to have for a later reference. it will make the task easier.
from there, as mentioned, its down to removing parts and cleaning all the passages.