The 1970 parts book, lists the same part number for the IH carb for both cubs and lo-boys, so it does not appear that there was a different carb used between the two, just a later carb used on later models. The 1954 parts book only lists one part number for the complete carb (the same as the first column in the page in Bob's post). So, if you just want to go for a period correct look, either IH part number in Bob's post should be fine. However, if you are trying to appease the "correct police," you want the 251 234 R94.
Eddie - a 1959 International Lo-Boy named after my father in law, who who bought her new.