you can try to put te3 in the mods folder
if it is not working update forge
1.6.2 mods will work in 1.6.4
If All of the mods you have use the SRG name obfuscation, and DON'T add world structures, then they should all work just fine. All Forge mods *should* be using SRG obf, if not yell at the mod author. And as for the Structures, basically if they add buildings to world gen. Say.. Village houses, nether towers, whatever, they will need to be updated. What I advise is you backup your save folder, and try loading it. If your game errors out, then one of your mods needs to be updated.