i understand that a 390 Gt and 352 4V use a 1.76 ratio rocker nonadjustable, are the numbers on them a way to identify them? I have set them up on surface plate and get about .010 difference from c/l of shaft to c/l of ball cup compared to the 1.73 rocker. Is this the only to tell them apart? I have one of each complete motors and a 66 merc 410 that i am putting the C6AE-R heads and rockers on. Thanks,,,,,,,