Statically, I think you are going to struggle to top Chavez/Cortes, who were 'officially' a combined 111-0: Chavez 67-0 and Cortes 44-0 in a 'title fight' and Chavez/Jakubowski in a non title fight: Chavez 87-0 and Jakubowski 37-0 (combining for 124-0).
Len Wickwar and Billy Bird deserve a nod. When they fought in July 1937 Bird came in with a known 226-63-16 record; Wickwar was 276-75-40...
Not as great in terms of numbers but still very impressive: Carlos Zarate 45(44)-0 v Alfonso Zamora 29(29)-0
yeah good shout i was looking through some records billy bird 226-63-16 vs Len Wickwar 276-75-40 kid azteca is similar i think bird vs wickwar is the highest though.
this was very normal for British fighters at the time, though these two were at the higher end of such figures. Most TOP British fighters fought in & around 200 fights, some many more and not all of them keeping proper record checks. But yes these were the kind of figures most of them were dealing with.
JC Chavez vs Buck Smith 102-4 vs 179-13 Maybe not the best, but surely close and remarkable for modern fighters.