On Saginaw rack and pinion gears built between 1988 and 1998 there were two different pinion ratios. Standard model gears had 2.1 inches of rack travel for each revolution of the pinion. The other R&P gears were sport models with 2.4 inches of travel for each revolution of the pinion (handling, sport, W56, Uplevel, etc). So you can take a ruler and have someone rotate the pinion (steering wheel) one complete revolution. Carefully measure how far the tie rod moves. That will tell you if you have a standard model (2.1 inches per rev) or a sport model gear that moves further-faster (2.4 inches per rev).
Now you also have to be aware that these same gears could have two different amounts of total travel. They could have 6 inches of total travel. Or they could have 5.7 inches of total travel. These gears can be identified by the total number of pinion revolutions or by just measuring the rack travel as the pinion is rotated full lock to full lock. Now 0.3 inches (just a hair more than 1/4 inch) doesn't sound like much. But it could make the difference of your tires hitting the fenders, frame, etc at full lock or not. So to be safe it would be best to find a R&P with the same total travel as the one you currently have in your Vette.
The standard model gears will have 2.7 to 2.9 number of revolutions of the pinion (or steering wheel) from full lock to full lock (depending upon the amount of total travel built into the gear). The sport models will have 2.3 to 2.5 total turns full lock to full lock.
So as you state your rack and pinion gear has exactly 2.5 revolutions full lock to full lock. This would mean that you have a sport model gear with 2.4 inches of travel per revolution. This would also mean that you also have 6 inches of total rack travel.
So you will want to find a standard model R&P gear from a 1988 through 1994 Cavaliar, Sunbird, Skyhawk, Skylark, Grand Am, Corsica, Beretta, or Achieva. These would be slower with 2.7 (5.7 inches of total travel) to 2.9 revolutions lock to lock (with 6.0 inches of travel).
I could be wrong but I think that all models of Saginaw R&P gears were fast ratio after 1994 so stay away from them.
Jim