Chewie - I sympathize with you as I see you are located in Michigan...harsh winters, damp moist climate, salty roads in the winter...so chances of finding a rust free Z ZX is almost non-existant. I lived in Ontario, Canada for over 15years and see what a few winters can do to perfectly good car.
If you are set in restoring that car and you are a great welder and hand person, then go for it...otherwise spend the extra $$ and get a clean rust free car from the West, Florida, Texas etc etc...
You have a LONG, UPHILL battle to fight to bring that car back, but good luck if you have your heart set on it.
Yasin