As with all collector cars, buying the best that you can afford within the budget you set is a good idea.
The better the car is so start with, the likelihood that you will be pleased with it increases.
90's are the most plentiful, and because of that, all else equal, will save you money without giving anything up.
Buy a color that you love, as it needs to be the dream car you see in your dreams.
Get help from a knowledgeable owner in your area, or actually near the car you are considering.
Better to have their years of experience working for you rather than trying to instantly learn everything.
Start your search on the ZR-1 net Registry Forum.
Members cars are typically much better maintained, and most members have no interest in selling a problem child without either fixing it or disclosing what needs attention.
ASK FOR HELP HERE!!!
Best of luck!!!
The search is always fun!!!!
Marty