[SS427]

Jason,
I am not real up on the '66's but for starters, Look on the drivers side near where the linkage goes into the case. Look around for a VIN stamping. If there and it matches the car then procede to look on the transmission tag mounted on the passenger side. There should be a large letter 'C' on the left and another letter on the far right. If it is a 'A, C or H', then it is for a 396. If it is a 'B' it is for either a 427 or a police 396. Not all Turbo 400's had VIN stampings on them so do not be alarmed if there is none. If it is there but doesn't match the car's VIN, then the above doesn't matter. I do not believe there are any other differences to the car between a 396 and/or a 427 in '66.
Rick