Reply to "Questions on 2-railing Lionel 86-foot auto parts box cars"

Original cars with the sheet metal sprung trucks, swap for atlas.
The newer trucks that can be converted, use the conversion kit.  
If you use the conversion kit, you replace everything but the side frames with new parts.  It works pretty well.
These are beer cars, but I use the 86’ boxcar coupler pockets on them as they should have cushion pockets and Lionel doesn’t supply them with the beer cars.
The swoosh car is the Lionel conversion kit. The circle cross car is atlas 70T trucks.  Both screwed to the bolster directly with the Lionel screws.  I used 1 micro mark shim to lower the coupler on both to the gauge height. The conversion kit car might ride a hair lower than the atlas trucks, but it also could just be the way the shell sits on the frame.  It’s not that much different.