Board Thread:Questions and Answers/@comment-24597759-20140227024418/@comment-23270394-20140307225723

Ah, I see the first forge version is for 1.5.1, shame. Anyway, on mods that are non forge, try putting the .jar files in the modpack.jar (and don't delete the META-INF). It will most likely crash, and if it does, post the crash log.