[Mr70]

It's a service replacement.
The "C" stands for Chevrolet.
The "T" stands for Transmission.
The "8" means it was assembled in 1968.
#42989th unit produced from the Muncie,Indiana plant.
They started those at serial #35000 and ended at #44999 at Muncie plant.
Thats a 1969 model year notated on the Trans.,so that August month code could be either August 1968 or August 1969,seeing as they stretched the 1969 Camaro production longer then usual.
One could argue it was August 1969,based on that late serial number of #42989 out of only 44999 made there.