A lot of the early W111 wheels were 13". Sometime in 1967 most Mercedes switched to 14" wheels. The first series steel wheels for the 230SL were 14" streel, 113 400 00 06, and 113 400 03 06. Your 280SL steel wheels would have used full wheel covers. Several different 14" steel wheels from MB models of that era will work, as they all used the full wheel covers. Look for 108 400 03 02 or 108 400 00 02. I believe only the later versions of the W111 coupes and cabs used a 14" wheel. 14" steel wheels off V-8 sedans of the era can be used also, since they used the same full wheel covers. These wheels are 1/2" wider and some have cooling fins built into the inside of the wheels to circulate more air. The later factory workshop manual has good descriptions, photos and part numbers for all of them.