hi willys and welcome ,
my deere has an 18" by 36" auger housing and has an 4 1/4" pulley on the engine and an 8" pulley on the outside of the blower housing............
the 8" pulley on the outside of the housing is on a shaft that connects to a 3" gear inside the housing ....the chain runs to an 7 1/4" gear on the auger shaft...................
the engine runs at 3600 rpm........................and i can toss snow almost 20'
if you need the teeth count on the gears i can check that for you , let me know...............
hope this helps you some,
bill
ps............. this tractor came with an 8 hp kohler but after using it , i would recommend bigger...........