63 Dodge Dart, now let me see;)
The measurement on this A904 represents the distance from the lip of the bell housing to the transmission mount bolts which is 22.75. It's the same distance from the lip on the manual bell housing to the transmission mount. I see no reason to connect the slant 6 engine to the manual trans setup in a mock up sense. Mine has the original slant six K member so all should be well. Looks different in the picture, but is 22.75, plus there is some slop in the transmission mount to move forward or backward a tad.