I had a 23 foot with 14 inch wheels and the "C rated" tires that just did not hold up.
Take one wheel to a dealer of aluminum wheels. They will tell you which wheels they have that will fit that five lug nut pattern. I believe it was some Ford 15" that would work. After I needed to replace the tires on the original 14" wheels, I want back and they had sold all of the wheels that would have fit. They were removed from a group of cars and other wheels were used was what I recall. They searched their current catalogue and could not find the wheel that would work.
I sold the 23' trailer and the information was in the warranty bag, but it takes a wheel shop just minutes to tell you which wheels will work. Airstream in Jackson Center also had the specifics of how the wheel centers on the drum. It was not as simple as you would think, but can be done. I wanted the 15" wheels for the "D rated" tires. The 14" are "C rated" and easy to puncture if you encountered gravel on a hard surface. Now with a 25' AS I paid dearly to get those wheels!