I'm not so sure about that. All the non adjustable rockers I've seen have been the 1.73 ratio and adjustables at 1.76. Any size compensation on the non adjustables was corrected with different length pushrods. It's possible one set could be aftermarket possibly. I know for a fact the Crane adjustables have a slightly different ratio than the oem and require a little long pushrod. You would think they tell you this BEFORE you get them. The oem rockers I have all use a 7 digit number. Some of the oddball ones have a 69 on them and probably might be aftermarket. I've never really gave it much thought. G.