When did "Rusty Jones" rustproofing services become unavailable? I
need to know until what date a 1989 wagoneer in central PA could have
been treated with this rustproofing on the frame.

The most recent mention of Rusty Jones Inc. that I could find was this, in 1998:

"Rusty Jones Inc. has filed for protection from creditors in United
States Bankruptcy Court here, saying that its car-rustproofing
business had deteriorated as American automobile makers extended their
warranties against rust. The filing Monday under Chapter 11 of the
Federal Bankruptcy Code seeks time for the Chicago-based company to
reorganize.

The Rusty Jones warranty program remains in effect for cars initially
treated before Aug. 1, but claims brought by car owners will become
part of the bankruptcy proceedings, the company's president, Charles
Wortman, said. Since 1985, Rusty Jones has seen its distribution
network dwindle to about 1,800 new-car dealerships in the Northeast,
Midwest and Florida, from 3,000."

http://query.nytimes.com/gst/fullpage.html?res=940DE1DD1F3EF934A35751C1A96E948260

I think I see a typo Pink. Did you mean to say December 7, 1988?

Thanks for catching my blooper, tutuzdad. It is indeed 1988.