I have a feeling it's the 63 tranny and they tryed to put the 70's block on it! I have a tranny out of a 75 duster,will the internals from the 63 switch to the 75, valve bodie and such? The 63 tranny is a new rebuild and the 75 is a working old tranny, I would like to get the new stuff into the tranny that will work with the engine.

TF

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Even in moderation i am excessive!

The parts will not swap from one case, into the other.
If you use the 68 and newer transmission, you will have to change away from the pushbutton / cable shift linkage and swap over to a machanical shifter. The speedo cable and driveshaft will also be different.

There is no reason why you can not use the 63's pushbutton (small hub converter) trans behind the later "big hub" engine, just use the adaptor ring.
DD