Harry Baggs

OHAI THERE, First off I wanna apologize if this is in the wrong section. Its tekkit classic specific so... I felt it should go here. My Question is what mods and versions are inside the modpack.jar for tekkit classic. The reason I ask this is because I wanna patch in a few custom things for my private server, I am aware of the custom pack feature now but I don't think it would be able to overwrite some base classes, which is what I need to do... sadly... If you know of a way to decompile the modpack.jar and deobf it so I can use it as a something to build off that would be even better XD. Thanks in advance.