Alas and alack!!! I just did a random check of my eguipment in regard to retro fitting frames. I found that, all of my box cars, flat cars and gons have a separate floor/frame and thus are candidates. However, hoppers, closed hoppers and tank cars do not all have a separate frame and will need something more complex than a simple frame switch. The frameless tank cars where the car body provides the support would require an especially more complicated solution.