Has anyone here ever converted a car with a pedal e-break to a stick e-break? I would like to see how much of a pain it will be if anyone has.

I would use as much of the factory components as possible. I also don't understand why the later gtps never had them?

It is not overly difficult to do.  Just have to change out the front cable usually to a shorter one and route the cable.  Ensure that there is the proper tension on the cable.  All of the mechanics are in the handle assembly.  Fiero hand brakes are popular for the hotrod crowds.