under dash wire harness

Air shocks are not a great a bandaid. So when you get 'round to it...new springs and shocks will be good.

Parking brake switch ought to have been protected by a fuse. Look into what wires burned or got damaged.

I agree with pretty everything above. I've become less of a fan of dielectric grease on the connectors. Seen where oxidation occurs (turns the grease green) even with the grease. DeOxit is pretty good. The 5% can be left on the terminal as a protective. The bulkhead connectors have a foam seal in them. Replace those if they've dried out.

There's been some posts this winter about testing gages. Take a look at those. It could be something simple like a poor connection. After visual and physcal check, You can do a quick test for gage resistance and if those are OK, attach resistors to simulate sending units and connect the IVR to a 12 v source.