..no, the "MX" and the C6 are quite different. The MX series (small, medium and large case, so named for the lengths) have cast iron center sections and removable bellhousings and tail shafts. The C6 is an all aluminum case with integral bellhousing. The C6 appeared in the 66 model year. Prior to that the large case MX was the heaviest duty FoMoCo slushbox tranny.
The austronaut 427 Cobra had one installed behind a Lincoln 462 engine when the FE was stolen out of the car. Don't have the registry handy to look up the CSX number.
Rick
