I have a muncie that is not like any of the others I have it has fine spline input shaft and has what I believe to have turbo 400 output shaft it also has drain plug on right hand side is this a rockcrusher or could it be something else

Probabily just a late Muncie. Take the side cover off and see if the angle on the gears looks different from any other 4spd you have ever looked at.

ALL late 70-74 ("661" main case) Muncies have the 26 spline input/32 spline output, and the drain plug.
Check the letter suffix following the date code.
Located on the pass side mid section of the case.
Starts with PXXX A, B, or C.
A= M-20 B= M-21, C- M-22.
Of course this is not for certain, as anything could have happened over the last 30+ yrs.
Only way to be sure, is to remove the side cover, and look at the gears.