Hi all, I'm replacing chain and sprockets on my '72 350B Sport (6v). Am aware that the chain is a 428 size, but I see that there are varieties of 428, i.e. 428-126, 428-136 ... My guess is that the latter figure might be the outside width (e.g. 12.6mm, 13.6mm) - although I don't see why that dimension is important, perhaps for strength? Also, I'd like to get an X-ring or O-ring type, has anyone had any experience/problems with those on a 350B?