does anyone know how many different rear gears chevy used in the camaro set ups?

I believe they used a different gear set in each car they built...
So about 200,000(+) sets each year for the first couple years - :D

If you mean Gear Ratio's available, then it varied by year model.
But, depending on the year, there were about 4~12 different ratios available from the factory, sometimes in different ring-gear diameters.
Each ratio may be also available with Positraction. But, that also varied by ratio, axle and year model.
There were also gear sets that were available "Over-the-Counter" from dealers that were not listed in the option sheets.

Many of the good Camaro reference books will often have a listing of ratios and axle code numbers in them.


Hope this helps;
John

If you mean ratio...i believe there was 2.73, 3.08, 3.31, 3.55, 3.73, (optional 4.10, 4.56, 4.88)