C&G (800/266-0470) shows stainless guards as 51A-16340/50-SS, $175/pair, That is $25 more than the rubber type. Of course, they are not stock, so can't be used on judged cars. I've never seen ribbed stainless guards, but they can tell you if they are. My '47 has the rubber guards from Drake. Nice pieces, but have metric studs. If you buy those, you will have to hunt for metric nuts.