Here is a version for Postbox only. It will not work in Thunderbird unless you are very retro and using Thunderbird 2.
A few things..
Postbox/TB2 does not allow extra fields to be added to address book. So only the basic address book field can be used.
Because of above, there is no room for a server ID. I have used Custom 3 for this.
There does not seem to be a unique card ID. I have created on in Custom 4.
Can not get Card by value other than email address. So a lot of crawling through the address book takes place on a first sync. Be patient. On first setup I would suggest setting autosync to 0. Doing a manual sync and waiting. Any sync after this will be much quicker. Do not set autosync to less than 5.
Please test.
Mark