Ok, the new distributor is installed and the truck runs. Still has difficulty starting, but I found a video channel by a guy in South Africa who knows Webers very well. He lists 5 things to check. I think my problem could be either distributor advance, or vacuum leak. Here is the video and his channel, which seems to be excellent: https://www.youtube.com/watch?v=t-VCi1lS8vU

Any thoughts?