I went through this recently and wanted to give a list of the required parts and years that I know will work.
I only looked at the GS550L rear wheels. 1981 and 1982 will NOT work. The drum is too large and the sprocket bolt pattern diameter is too small. I recieved a 1983 GS550L wheel and it worked perfectly. 1983 through 1986 all have the exact same sizes according to oem website. Check measurements! I list the two important ones later. What you need to buy is the wheel with the rubber sprocket bumpers (shock absorbers) in place. You will also need the sprocket hub (retainer drum). This is the part that the sprocket bolts on to and fits into the bumpers. The retainers(part 12) measured to be the same as the S40 so you may not need them. The bolts in the sprocket are different than the S40 so you need these too.
Everything in parentheses above is what the oem website calls them:
https://www.suzukipartshouse.com/oemparts/a/suz/50d3f871f8700230d8b4cf0c/rear...So you will use the drum brake, spacers, axle rod, pulley, and left end bolt and washer from the S40. The sprocket hub from the GS550L will be bolted with GS550L bolts to the S40 pulley. Everything goes back on the bike the same way it came off.
There are probably other wheels that work, but I can confirm this one. Make sure when buying the wheel you check that the drum brake reads 160.7mm as max size and the bolt diameter on the sprocket is 100mm. Also, make sure the bearings are still all good or buy new ones.
I know there are experts who know a TON more about this than me, but feel free to ask me any questions.
I am attaching a pic of the bike with the wheel. Thanks.