A little tricky because they're (like most any Lionel) not meant to be disassembled by us hoi poloi, but there are tiny holes to release the respective latch tabs on the plates the trucks ride on using a very small allen key or small diameter handled thrust punch. See photo of bottom, 2 holes catercorner to opposite truck journals. Given the lack of a carbody bolster and my project timetable I used the K-Line 2-rail trucks with their 36' wheels and high truck bolster and shimmed the Kadee box down to compensate. I haven't touched it since, as it's way down on my list.
Replacing the roof walk and ladders would be a big improvement, I have a kit bashed Weaver 4-bay with the PRB grated walks and it's a better model.
I did a "mass" set of 2 rail jobs on some Lionel and K-Line's (and lots of grafitti( for a Conrail Freight I put together for the TCA show a couple of years ago using a Trainman GP-15 and U-23 (our modular club was the token 2 rail lobby layout) I bought this car at local shop's firesale closeout to resell but liked the factory scheme so much I kept it, pretty sure it's no good for this type car, but still.....
Hope this helps, agree these are great car bodies.
Pete