1976 CB750A Hondamatic carb rebuilding?

I rescued this bike from a barn in north Florida, she is an early 1976 CB750A...I has been sitting since 1995 and will less then 30 mins invested I got her running...She is leaking gas from the carbs and the oil is like tar even after 3 oil changes (run 15 mins between changes)...The local honda dealer says there is NO rebuild kit for the carbs...I find this odd..the 1976 has 24mm carbs and the 1977 and 1978 have 28mm carbs..if anyone knows if the kits are interchancable please let me know..the dealer says once they are open I cant return the kits.Any leeds on website for these bike would also be a big help...thanks...