A lot depends on precise you want to be. I was under the impression, this was to a representation not an accurate model of a prototype. The ribbed sides make that hard. so my power truck suggestions were based on pretty loose criteria.
Another power truck option that I mentioned before was used quite commonly for the walthers kits and others. This was the single power truck that General Models and later All Nation used to power their NW2 diesels. They are similar to the modern trucks with motor on truck, but perhaps a little shorter wheelbased for the NW2. These are not popular among modelers and therefore if you find one at a show the price should be right. They were sturdy and should clean up well.
I like the idea of the commonweath express truck for the rear unpowered one.
