Steve,
I don't know if the "S" was a first or second year model, although the monthly records do list the 482-982 including the 582 Special for the months of Nov 1980 thru the end, they do not list the tractor model number from Nov 1979 thru Oct 1980. The reports show that the last IH 482 and 982 were built in Feb 1981, the last IH 582, 582 Special, 682 and 782 were built in Apr 1981. The last IH built Cub Cadet 82 series was a 782, S/N 694248. The last 38" mower deck was S/N 132759, 44" was 162093, and last 50" was 137635. It's the wrong page, but the last 182 Cadet lawn tractor was S/N 50645, Mar 81, last 282 was 49203, Jan 81, and last 382 (doesn't specify if it was a Hydro or gear) was 50978, Apr 81
All of this except for the Cadet Lawn tractor info can be found in the FAQ's, item # 28