Read the full article on Hagerty.com: https://www.hagerty.com/media/videos/davin-works-on-our-buick-straight-8-at-home/
I love Davin's use of old towels (or new). I find them perfect for working at the bench. A used towel never goes into the trash!
You even can find them at thrift stores--nice ones, for the cheap. They buffer the more fragile parts and they soak all sort of grease and oil. jay
Regarding the fuel pump diaphragm--can't you actuate the lever to add tension to the diaphragm so that it will not flip around but will sit nicely on the pump housing during final assembly? Working with vintage Volkswagen fuel pumps, we find that it is necessary to bolt the fuel pump to a jig which presses the lever enough so that the diaphragm tension is pre-set. Thus, two things are accomplished at once--tension is pre-set with the diaphragm sitting flat in its spot--and all screws go in without any jiggling.