They did sell some of these ready to go for 3 rail. They used Weaver trucks. They used a bonded washer to raise the height of the car to gain clearance for the truck to pivot. The Atlas truck would probably need a lot more work to mount. The height is much lower than the Weaver. Weaver trucks are scarce if you are looking for the diecast ones. Anything is do able. Factor in the cost of the car and buying the trucks. Then price out old Atlas stock. Atlas re did some Intermountain cars in their Masterline. With Atlas you get the added benefit of a die cast chassis and a more rugged car. The Atlas detail as fragile as it may seem. Is more durable than Intermountains.
If you want to go the easiest and least costly route. I would use Weaver's plastic trucks. You should be able to come up with the trucks at a good price. Many upgraded their cars to diecast. Their should be a surplus of the plastic ones around. A lot of guys adding Kadee's to Weavers. I was pretty much giving away die cast couplers.
