You got brain fog on the manual as it does list the KT725. KT715-KT745 list is saying including all model from KT715 to KT745 and if I am thinking right 725 is between 715 and 745 but maybe math has changed that much.
Second not all websites have all the engines listed. For your engine go to Partstree or simply Google KT725-3083. That specs is a valid spec number and is list as MTD spec'd engine which Cub Cadet is one.
Your spec uses the 32 083 09-S air filter with the 32 083 10-S prefilter.