Old world blues (Help please)

[Famout]

Me and friends had a tekkit server running for the past verison and made quite a bit of progress in it. After waiting a little while for the current release to become stable we decided to update, but found out it does not seem to like our old world, since any time we try to join the server gives an "end of stream" error.

 

Now when joining a new world it does work fine, and I am aware it is recommended to use a new world, but is there anyway to just transfer over things from the old to the new? We already lost all progress once before due to stupidity, and I doubt everyone wants to rebuild their bases from scratch. Heck I think they would be happy if we could just set up a way to transfer items alone.

 

As a side note, what is the best method of automatic backups? We found a plugin for the last server, but it made a silly amount and started taking up 1TB+ worth of backups when left to itself.