5K is too much for that kind of model.
It should be below 3K
You can easily reduce polygons on wheel "wings" and cabin sides without loss to visual quality, cut all windows with alpha-channel on texture, the wheel sides, headlights glass and other similar parts can be made of square/rectangle, with required shape cut by alpha as well.
Also see modeling example here:
http://files.games.1c.ru/_/TOW/Model_M6.zip
You may also ask for requirements at the "Theater of War" forums. They are very similar to ones for the SoW vehicles.