View attachment 1377673
The internals under the cover. I can't find the other picture I have that shows different cover orientation for E bodies vs B bodies.. but this drawing shows where it should be on a B body.
Put some tape on the wiper arm mounting shafts and mark a line. Turn the wipers on and make sure they only go back and forth for that 95 degree or so sweep. If so from that you can then determine where the arms should mount and correctly sweep the glass (but don't put them on!). Then you can sort out why the assembly is parking at the wrong end of the rotation. Maybe that "new" motor has been assembled wrong.