I have four 500's. Three 83's and a '84. Plus, five 82-83 250's. All run and are ridden. They win they're share of the vintage races.
Lost a really nice '82 465 (and a 250) to thievery at mid-Ohio in '07.
I have little trouble at all finding parts. Lots of stuff was shared between the 125s, 250's, 465's and 500's chassis-wise.
The '84 had some slight differences, especially in that wonderful full-floater suspension/swingarm, but otherwise very similar to previous versions.
Suzuki offered the 500 through 1985...with a front disc, available in Canada but not USA.