Hate to break it to ya, but just cause the bike is an 83 doesn't mean SM wheels are going to be any cheaper than if you had a brand new bike. The rear wheel's old style cush hub/drum brake is whats going to keep it from under $500.
When I built the wheels for my XL I went the cheapest way possible and still dropped a grand.
If you want both SM and dirt and keep it easy swapping between them, you'll need:
another set of OEM wheel hubs = $100 min
extra front rotor = $25
extra rear sprocket = $40
set of Buchanan HD spokes and nipples = $100 min
excel front rim = $150-200
excel rear rim = $200
HD tubes = $80
set of tires = $200-300
labor:$150 or you could build a truing stand and lace them yourself.
This setup is by far the easiest to build, swap and maintain.
You could build the wheels from GS500, CBR F2, as well as a few other bikes but I'm not sure you WON'T need to machine or modify them to work. The excels with new spokes laced to stock hubs will be the lightest wheel set you can find or build.
FWIW: When I sold my set to another SMJ member I still got $800 for them.