Sometime manufacturers run small runs of parts to see if they will sell or are in need. I'd contact the places you saw them and email or call customer service and see what they can find.
On the diagnostics, you will probly need the GM tech manual for that specific year/make/model.
Check fleabay for used manuals, or Alldata online manuals.
I'd start by inspecting the wires to the shocks and check the shafts on them to see if they are rusty or chewed up.
I dont think I've even had to deal with this crazy system and I have worked on a few in my day.
I'm trying to get my hands on this 69' GS Convert a friend has.....
Nice little 327vette motor , B&B pushing around 400hp +/-.
He's asking $5k and it need a top and some body work.....
hope that helps.