I'm a 4 speed guy, is there an instance where the aluminum cases on these are so old that they cant be rebuilt any more? doesn't the sprag "spline in" to the case? I am vaguely familiar with the insides of a TF but it probably has been since the 90s that I've been in one. I may be thinking of the GM Turbo 350 with the center support splining in to the case.
It goes without saying that i think that Chrysler would be badass with a 4 speed even being the heavy car that is is...:)
