Any mfg 2 rail trucks can be made to work on any mfg cars. some just require a lot more work, some are drop in.
The NMRA (national Model Railroad Association) developed standards for models to be interchangeable in 1930s and 40s. Track gauge and wheelgauge for example. But a major standard is the distance from the top of the rail to the underbody of the car. This affects coupler height. If the car is at this height, then if you mount kadees, they will be at the right height and work with all other cars that follow the standard.
Another set of standards is the distance from the top or the rail to the bolster where the truck mounts on the underside of the car car and the height of the bolster on the truck above the top of the rail. If these standards are followed, by the truck mfg and the car mfg, then mounting the truck on the car will result in the car underbody being at the right on the rails.
Most 2 rail mfg are small operations and rely on each other to complete the products needed rather than having all things for a complete model RR. Therefore they generally build to NMRA standards.
Unfortunately most predominently 3 rail mfg ignore most of the standards. They seem to have a business model that tries to entice you to buy all your products from control systems to locos to cars and track from one mfg. For this reason, they all use different truck mounting heights, bolster sizes, and ways to mount the trucks.
Mounting Atlas, Lionel, or MTH trucks on other mfg cars is more work than just switching trucks. Bolsters have to changed or modified, holes in truck bolsters have to be changed, and new mounting screws are often needed.
When dealing with these 3 rail cars, I have found in most cases I can disassemble the truck and just replace the wheel sets with intermountain or Athearn wheel sets and reuse the rest of the truck. It greatly simplifies conversion. Often the 3 rail coupler mounting tab needs to be cut off too. MTH and Atlas trucks can be disassembled with a screwdriver. Lionel requires drillilng out rivets. All require care taking the springs out and putting them back which a new subject.
I have had very good experience with plastic trucks and metal wheels and/or axles. the plastic used in trucks is "engineering plastic" (delrin is a brand). It is very slippery self lubricating, so metal axles roll very freely in it. It takes injection molding very well but does not glue well. It is the kind of material used in bearings in mfg where slide bearings are common such as clamps for fixtures etc. I also still use a lot of Athearn delrin wheel sets successfully.
