Ralph Berg said:
As you can see from the pictures, the trucks are easily removed from the body.
After that, things become much more difficult
Ralph,
A few years ago I converted a Lionel 616 Zephyr set to run on my 2-rail O-gauge layout. The easiest way was to replace the wheels with new, modern, insulated ones. You could probably find some wheels that would fit. I used NWSL brass bearings in the truck frame as the holes were way too big.
But looking at your photos, I suggest you just need new axles and a spacer. Your local R/C store can supply a variety of steel rod - one will match what you have. Then get some plastic tubing - I use the stuff from my wife’s new shoes - and cut it to length, about 1.56". I’d cut it a bit small and get some plastic washers to adjust the gauge as those wheels have big flanges. If the tube isn’t a tight fit on the axle, you can wind some electrical tape on it to make it stay where you want it.
You don’t have to worry about the outside of the wheel, as it will be kept in place by the rails. You may need a washer to keep them centered.
A cut-off wheel in a Dremel tool will make short work of the steel rod, and will allow you to cut the end of the axle to free it from the truck.
I could do it for you, but it isn’t very complicated. How many cars do you have?