Also check the
JMT forum on Yahoo Groups. They have a spreadsheet for organizing resupply with a packer service to help group people up. It's set up for a different trail junction (Baxter Pass?), but you should be able to adjust your schedule, as Salty wrote. Bishop Pass is not well located for resupply for a "typical" JMT schedule. We were there in less than 2 days from Muir Trail Ranch just last week.
