i had a 1966 GTO in high school. a complete restoration. as a young kid i was told i need a different transmission to make it faster. i took out the original automatic transmission and replaced it with a turbo 400. i still have the original automatic transmission and im not using it. its the ORIGINAL trans. its been sitting for a while and will need to be gone through but it never had any issues in the car. i no longer have the car, i contacted the owner and he is not interested in the original trans. best offer takes it. i can send pics to you. just contact me.