Help Modifying Cerrain In-game Map DATs

Hello, I've been dabbling with adding a few additional labels to my in-game maps for personal use by editing the DATs via Tex Hammer/Photoshop.
It's all smooth sailing with the exception of certain maps like Bastok Markets, Port Bastok etc as they seem to use? palette? textures? as opposed to the usual dxt3 that is easily exported/imported.
Would anyone be able to point me in the right direction importing my modified map pngs into the corresponding DATs for palette? Based maps? (I've tried importing just the png but it distorts the colors for certain things so I'm not sure that's the solution.)
Thank you.