Yeah, the '89 Corvette was the first to use the bullet proof ZF 6 speed, it was supposed to be launched in the 1989 ZR-1, but due to production delays the ZR-1 only made it's debut in 1990. GM decided to test the ZF tranny with the '89. The skip shift feature took a bit of getting used to, with engine warm, between 12 and 19 mph and throttle at less than 35%, second gear is locked out and you are directed straight to forth gear, otherwise, the gear change is very positive. I know the 1967 Alfa Romeo Stradale had a 6 speed, but that was a race car for the street, only made a handful, don't know of any others.
Seems yours is a bit of a hot rod!
....just caught on to your login....clever