If you want to run a true sequential manual gearbox, try

http://www.xtrac.com or

http://www.quaifeamerica.com/

The C5 Z06 uses the same T-56 Tremec as the Viper, Aston Martin Vantage and the Ford Mustang Cobra.

Some would not consider the Tremec T-56 a true racing transmission as it is not a sequential manual gearbox with shift without lift, or SWOL. The engine control unit allows the transmission to shift gears without the driver lifting off the accelerator. This feature is on some of the Xtrac's. That's not to say that one cannot have alot of fun with a properly set-up Tremec. The Tremec TKO seems more robust than the T-56.

Some people use the following Quaife tranny on a Dodge Viper:

QUAIFE 6-Speed HD Sequential Racing Gearbox

6 speed with sequential selection
Dog engagement, straight cut gears
Wide gears on 90mm centers and larger bearings for additional strength
Quaife bellhousing for direct fitment on Viper (starter relocated)
Optional digital gear position display
Various ratios available
33G RWD Base Ratios
2.432 1.803 1.368 1.105 0.935 0.819

QUAIFE 33G 6-Speed Sequential RWD gearbox 00.300.160 $16,195.00

Bellhousing for Dodge Viper Q264 1,375.00

modifications to customer's bellhousing, from: 625.00

Optional digital gear position display 00.900.100 875.00

I do not know if you want a syncho tranny but a racing car dispenses with such refinements. It has big, square teeth that engage noisily and rely on the skill of the driver to bring their relative speeds close enough to allow engagement.

There is alot of info on sequential manual transmissions on the internet. Not all are as brutish and expensive as the Quaife. It is a matter of finding one that fits your driving ability and budget.