How to change Block IDs?

[Sgt Phantomizer]

Somewhere i read that this is done on the config file for the mod in question, but is this the case for every mod? or does it vary from mod to mod?

Me and my friends would like to integrate the Forestry mod back into Tekkit Lite for our server as well as as add the Xtra Blocks mod and maybe a few others, but it always comes back to whatever we add not being compatible with Tekkit because the Block IDs are shared between one mod or another.

Anyways, how do you go about doing this?

[RalphRoberts]

http://lmgtfy.com/?q=how to change block id's in minecraft

-_-