I have been playing a barb on 1.03 and it is really slow, can only pay on players setting 1, the drops are very minimal and do not match up with the drops in later patches. Like a unique might drop a magic club and a minor healing potion.
Champions and unique monsters in classic (1.00-1.06) will only drop a potion and gold, or a potion and a magic item. Magic find only works on normal monsters, not champions, or act bosses. The exception is in act 4 where champions and uniques have a fixed 12.5% chance to drop a rare. Act bosses are not worth running at all as the drops are pitiful.
This means the best strategy for finding rares is to load up with magic find and kill as many normal monsters as possible plus any uniques and champions, typically in the river of flame or chaos sanctuary. That is, of course, unless you are running 1.00 and then in that case you need to kill the cow king over and over.
Starting in a classic patch other than 1.00 is pretty difficult. But in 1.00 with unlimited cow king drops, you can just beat normal and run cows until you find some decent gear and then continue on to nightmare (same with heck).
Tips for spending hundreds of hours killing the cow king over and over are:
-You'll be able to find sojs relatively easily once you have a manald and a nagel in the stash
-You can keep wormskull and the undead crown in your stash to get failed unique rares pretty reliably (and other item types too, just that rare bone helms and crowns are pretty desirable helms imo)
-The cow king's drops are able to be manipulated somewhat by map seed selection, and character movement (same as 1.07 racks, if you run around the map in the same way, you can get some of the same items to drop. takes a lot of practice)