Can add the waterberg in Limpopo to this as well. Also certain areas in Namibia...
Also keep in mind that a 60" kudu especially a 60" kudu hunt is no cake walk and success rates are low under fair chase conditions....
Hunting the correct areas as far as genetic history such as the soutpansberg, waterberg and spots in Namibia are concerned is a good start.
There are operations that will sell you a 60" kudu but wether or not.. you will be satisfied with the hunting aspect is a entirely different subject to consider.
Remember to ask pertinent questions with regards to hunting conditions, size of specifically the area you will be hunting(not concession size) but rather the particular ranch you will be hunting, especially if you are serious as far as the hunting aspect is concerned,
Good luck and I hope you enjoy your safari
My best always.