We used to use racing wheels to get them to fit inside the narrow wheel pants. There is a source that was mentioned on here, but I can't find it. H^^Luckily I still have three sets of them. Two installed on my Cobra and on an Ares.
type in "racing wheels " in the search box. Lots of info there.
Racing wheels work well, except for the 'knife-edge' tread look. I used some oversized ones, (3") chucked them in my electric die grinder, and took off 1/4" on the belt sander, shaping them as I went. Looked good.
For my Golden Age stuff, (Gee Bees, Mystery Ship, etc.) I use Williams Bros. 'Golden Age', as they are scale spokes with simulated fabric covering. They allow a narrow, scale pant.
That said, the Mystery Ship has pants big enough to be worn by Homies! (these would allow a wider tire...but I still used the Wms. Bros. Golden Age type, bushed with brass)