I am thinking of swapping out some rivarossi passenger car wheel sets. Are they 33" or 36"? Look like 36" to me.
I believe the Rivarossi wheels are 33" but look larger because of the flanges. You can replace them with Intermountain 36" wheels but you have to shave off some of the brake shoes becaues they will drag against the larger wheels.
Also there are areas on the truck frames where the brake shoes attach to it that have to be cut away to clear the 36" wheels. A sharp Xacto knife or a Dremel with a diamond coated burr work well for this.