That's quite a jump from 2.56 to 3.55. Guess it depends on what trans and diameter tires you have?
From what I've seen all Firebird BOP 10-bolt axles are 28 spline. When I had mine apart, the axles did not have c-clips and they're not shown in the factory manual. If I recall only the GM 12-bolt used c-clips. re: speedo gears: search google for pontiac speedo gears by color - numerous sources come up.
