I am woefully short of box cars for the 1:20 operations I’ve set up, I don’t have the budget to buy more RTR cars, nor the time or part resources to build the basic kits I already own. What I have are several 1:24 scale Aristo/Delton boxcars. They are tiny compared to an AMS or Bachman 1:20 box car. I hadn’t considered using them as-is until I saw this picture…
That inspired me to try one in a 1:20 train. The stock truck mounted couplers don’t line up with my 1:20 body mounts, so for a road test I cobbled up a Bachman 1:20 coupler on top of the truck mount tang. It worked well enough to tow the car but looked horrible. I already know from my up-scale project that it’s pretty simple to body mount an Accucraft coupler under the Delton frame using a PVC mounting block…
So this leaves me at a decision point. Unless I make one a transition car, once modified these cars will no longer couple with my 1:24/1:29 trains. The modification will be reversible since I wont be using the side beams like in the above picture. If the coupler is removed, I can swing the truck back around and put the truck mount coupler back on. Only the mounting pad would remain. I just need to bite the bullet and start gluing and screwing 
Technically, I should also up-size all of the hardware, but when I put the Delton car next to the 1:20 car I built last winter, the difference in hardware isn’t noticeable to me. This could be because the Delton details are a bit clunky to begin with.
