So, if you look at the groove inside the rocker you can see it does not intersect the oil bleed hole. This means this is the correct rocker for a 59 up 235 ( the oil system was changed in I think 59 to make it a little more of a pressurized system). So, you need a number 5 rocker for 59 and up 235. I just checked my box of used rockers and don't have a 59 up, just 55-57, but at any rate that is what you need, 5 with an offset grove.
