While you can’t just move TQ content into the GD, most of the TQ assets are compatible with the GD engine. The minimum requirement for models import is updating the model version by changing one HEX value ([TUT] How to import Titan Quest models into the editor).
As stated above, TQ gear is not compatible with the GD player’s skeleton, however this does not apply to weapons and shields that do not use skeletal animation. To transfer the rest of the equipment you really need a 3d editor and the easiest items to transfer (after weapons) are the helmets which require only one bone to be attached, everything else will require 3d modeling practice.