ez projects / ezupgrade / news / now supporting upgrades 3.5...
eZ Upgrade has been extended, supporting upgrades of eZ installations as old as 3.5.0, and upgrading them up to 4.3.0.
Now there's no excuse for not moving your 3.x site over to that shiny, new PHP 5 server. :)
This is as far back as eZ Upgrade will support versions eZ Publish versions.