I just replace the Lionel wheelsets with Athearn ones I have on hand and it works fine. I like the older trucks with metal bolsters the best. They are a little harder to work with since the rivets mounting the couplers have to drilled out. However, the advantage is if the new axles seem too loose, you can simply bend the metal bolster part that is screwed to the sideframe in toward the middle a little bit. It tightens things up.