I recently finished that project and had the exact same question. Since the tank is a reasonably close approximation of one the Texas & Pacific had in one of its Ft. Worth yards, I decided not to use them at all, but to follow a color photo (mid/late 40s) that shows the prototype with a large T&P diamond herald and nothing else. I’ll keep the decals and if other photos turn up suggesting placement, I MAY decide to use them.