Ed...It has always been my understanding that you could reverse either the field winding or the armature winding polarity but not both to change the rotation of a wound field DC motor. Should be doable .
I spoke with our local starter rebuild shop...he said only magnet motors can be reversed by rotating the magnets? I was going to try it anyway but after opening it the brushes need R&R and the fiber thrust washers need replacement - have no idea where to get them - but still looking. Do have an assortment of brushes that I can make work.
Not a big deal I have a couple of potential motor sources.