Ok, so I got 3 head mods:

All in one
Jedi_Killas
ShimaonsHeadMod11

Alright, so I can install one of these head mods, and it works fine. But, if I install another one it basically cancels the one before it out. I.E. I can install Shimons and it works then I will install the All in one head mod and Shimons does not work anymore, and it seems that the All In One Head Mod works over them all.

So far I have copied all of the rows in the .2da file from Jedikillas to the All in one 2da file, and still no luck.

Any help will be greatly appreciated.

They'll all use the appearance.2da file. You'll have to edit it in order to use them all. Someone else will have to help you with that, though - I don't know how to do it myself, much less walk someone else through it.

EDIT: Never mind. I should have read your entire post. Sorry.

I don't have the mods myself, but it sounds like they use either the appearence.2da file or the heads.2da file or both, if it is both your problem probably lies in the fact that the two .2da files reference each other by refering to one anothers line numbers

Any head mod will contain 3 2da files that will require merging. Appearance.2da, Heads.2da, & Portraits.2da. All 3 of these are relatively intertwined meaning if you copy the rows from 1 appearance.2da file to another you must make sure it's entries match those from the new lines in heads.2da and that the new portraits.2da files new lines match those of your new entries in appearance.2da. I would recomend using my making a new selectable head tutorial in the tutorials section. It includes pictures with the instructions.