Re: Late 50’s OMC extension kit for 5.5 or 7.5hp Home › Forum › Ask A Member › Late 50’s OMC extension kit for 5.5 or 7.5hp › Re: Late 50’s OMC extension kit for 5.5 or 7.5hp chinewalkerUS Member - 1 Year (includes $3 online payment fee)Replies: 459Topics: 15 September 4, 2018 at 2:00 pm #82265 There’s no reason at all why you couldn’t use a later 6hp style unit with a split shift rod.