Suspension is attached to the main model, only wheels and tracks have another texture.
Did you ever check out a FH2 Vehicle and its textures? This would have been an clever idea, because you would have seen how we did it.
You could even texture everything on one texture, if it comes to modeling it´s not important how you do it.
If it comes to how we did it, it´s mainbody on one texture, wheels and tracks on another.