Here is my usual and shameless plug for something VT lol.
Atlas did VTR PS-1 boxcars w/ 7’ door in HO and N but not O. They’ve done red and green, both with the silver roof which VTR kept when repainting these from Rutland. The red is prettier I think. Would go beautifully with your GMRC (subsidiary of VTR) GP9 and the VTR SD70Ms in production now.