Again, it's generally considered polite to ask permission rather than merely letting people know that you're going to be borrowing something of theirs .
...However, since UE is in itself a crazy collection of models from various sources, we do not particularly mind. You have to ensure that you give credit to everyone involved, because none of these particular models actually come from UE.
Scimitar - mesh from the XWA TC team (I don't know who was the author of this specific mesh, four possible people are Nalkri, Rogue_62095, Hawkeye, JC, and Hades), textures by Wildcat, based on XWA TC textures (again, not sure who made the XWA TC textures, but the possibilities are Hawkeye and dreddnott).
Salthi - mesh by Tigershark, textures by KillerWave based on Tigershark's original textures.
Gratha - mesh by XWA TC team (I think... it was a long time ago), and textures by... well probably Wildcat and the XWA TC team.