What is the width of cut? - not the width of the deck
Side or rear discharge?
Will guess your tractor is model 21-12K801 and a 312-8 Tractor
These are the decks sold in 1985 but older and newer decks also fit.
05-36MR03 36" Rear Discharge Mower
05-42MR03 42" Rear Discharge Mower
05-42MS04 42" Side Discharge Mower
05-48MS04 48" Side Discharge Mower
Good parts lists herehttp://www.partstree.com/parts/
Type Toro in the 2nd box and a model number in the 3rd box.
The parts that are priced are still available from any Toro dealer.
If you require more info Wheel Horse did publish charts showing the various spindle assemblies and their parts. Let us know and will link you to them.