Just installed FCOM, and what I thought was a flawless job by me. Unfortunately about 2 hours in, I noticed every clanfear's head is missing/stretched out across the room, so are the dresses of a lot of putrid hand members. Anyone have a solution to this?

Your error is a known issue. It has been discussed here many times, certainly in the last 2 weeks. Search the mod forum for clanfear and/or streched, filter by date if too many hits.

You need to delete some skeleton meshes in Data/meshes/creatures... I don't have the exact details ready right now. it's a problem that apparently was introduced by the UOP version 3.4.1.

As Tommy_H pointed out, delete meshes\creatures
clanfear from atafolder. You may also get this problem with daedroth so if you do, do the same, delete the meshes.

http://www.gamesas.com/topic/1252270-relzunofficial-oblivion-patch-uop-v340/page__view__findpost__p__19801640

The clannfear mesh is now fixed, thank you. I read that topic above and i realized it is not the putrid hand robes that are stretched, its the tails of a few argonians. I dont have TIE like the people in the post Turkeys linked did. Any suggestions?

Check if you are using any body replacers that include Argonians. Then remove them and see how it goes.

If no replacers, look in the loose files under meshes\characters\argonian and move those out to test and see how it is.

Finally, try using the maximum compatibility skeletons and see if that affects anything.

Body mods don't "include" Argonians, or better yet, they include "all" races. You cannot change meshes on a per-race basis, as all races use the same meshes. Only textures can be changed, and a body mod "not" providing fitting Argonian body textures while it replaced the body meshes "all" races will use would just have "destroyed" the entire Argonian race, and as such (hopefully) won't exist.

If it's only "a few" Argonians but not "all" there's also no use in removing "the race's" tail meshes, so they revert back to Vanilla. Best this can cause is the tails' textures no longer working on the now-wrong tail meshes.

The issue is originating from skeleton files being assigned "per actor", so you can very well have NPCs of a beast race which aren't using the beast skeletons, and as such are missing the tail bones. Vertices rigged to bones which aren't in the skeleton used will "not know where to stick to" (simply speaking) and just shoot off into infinity. The mod these Argonian NPCs come from is likely to blame for this, but it can very easily be fixed on your end by doing what Peter ID suggested last.

The Maximum Compatibility Skeleton package will install the same file for both beast and humanoid skeleton, and as such it won't matter anymore that the wrong skeleton was assigned for those NPCs. Of course you can do this yourself as well, just copy your "skeletonbeast.nif" over your "skeleton.nif", unless there are different skeleton replacers at work for both skeletons, then you could be loosing features from one by replacing it with the other.

The most compatible skeleton replacement I've seen so far is Growlf's Universal Skeleton. It includes all features which are inside the famous Maximum Compatibility Skeleton, plus several some more.