Allright, searching didn't show anything like this, so I'll post it here.
THIS IS NOT MY GUIDE, THIS IS FROM MADX MACHINIMA SITE. YOU DO NOT NEED TO REP ME FOR THIS, I AM NOT THE AUTHOR, I'M JUST POINTING THIS OUT.
This is a guide on how to convert models from 3D Studio Max to World of Warcraft.
Before we start I want to clarify something. You don’t need to modify ANY files from your WoW installation to make this possible. By using WowModelViewer you are able to use this for movie magic by not even toutching a single file created by Blizzard Entertainment. All files converted can (and in this example will) be stored in a new mpq file that you create! For starters, we need to create a model inside 3D Studio Max, or import one from another game. In this tutorial I have used a md5 mesh importer script to get the shotgun from Doom3 into 3D Studio Max. My goal is to get this gun inside World of Wacraft. Make sure that the grid is turned on in all viewports, and align the model so that the spot where the charecter would put his hand or fingers are in the center of the grid. Also be sure that the weapon points left when seeing it from the top viewport.
Now select the model and hit [FILE] -> [EXPORT SELECTED]
Select “.3ds” as output filetype, and hit ‘Save’ at the desired destination.
Now 3D Studio Max will ask if you want to preserve the texture coordinates. Hit “Yes”. Due to limitations in the 3ds format it might rename the texture file if needed. Remember to write that down, since that is the name you must have for the texture you import into World of Warcraft.
For WoW - 1.x: 3dstom2.exe is a commandline tool so you either need to make a batch file or open the command prompt. redir into the directory where the 3dstom2.exe is located. The syntax is 3dstom2.exe - 3ds_file_name - m2_file_name - Scale. For WoW - 2.x: 3dstom2TBC.exe is a commandline tool, so you either need to make a batch file or open the command prompt. redir into the directory where the 3dstom2.exe is located. The syntax is 3dstom2TBC.exe - 3ds_file_name - m2_file_name - Scale. My 3ds model is called hunter and since I can do the renaming in MyWarcraftStudio I just call the model Hunter.m2 and set the scale to 8. Now I already knew that the scale was 8, but you might need to experiment a bit to get your model in the right size.
To update a 1.x model into a 2.x model run m2TBC.exe and use the modelname as syntax; in my example m2TBC.exe hunter.m2 a new model will be created and that is the one you must use.
Now the model is converted and can be used inside World of Warcraft. We just need to include it in the data files. Open up MyWarcraftStudio and select [Pack] -> [Create MPQ], browse to your “World of Warcraft/data/” folder and save it as Patch-3.mpq
Now hit Pack again and select Import File, select the model, you will now be asked where to place the file. You might want to go into another mpq file to grab the location of the model you want to swap. In this case I want to swap that rifle that the new hunter dwarfs start with, so I set it to “Item/ObjectComponents/Weapon/Firearm_2h_rifle_a_01.m2″. If your model got a texture place it in the root folder, like here w_shotgu.blp.
Save the file, go into WowModelViewer and enjoy your new weapon. You cannot run World Of Warcraft now since the model file does not match the hashtable (security stuff), so unless you know how to ModelChange ingame you wont be able to run World of Warcraft while the Patch-3.mpq is in the data folder. So when finished you can go and rename the file to patch-3.mpq.old so World of Warcraft will ignore it. Here is a example of how that gun will look ingame: Note that the 3ds format got almost no animation support. So even tho it looks cool it doesn't move.
3dstom2.exe
M2TBC.exe
Some people seem to have problems with the 3dstom2tbc so i have taken it down to fix the problem. You can however still do the convertion to 2.x by first using 3dstom2.exe and then update the model with M2TBC.
Thanks to Cryect for the original 3dstom2 source code and nintoxicated for refrence to creation of M2TBC.
YOUTUBE EXAMPLE
Peace.