I got it off tonight. Just took some patience and some more appropriate tools. I started with a couple of chisels to get it to move a little. Then used a variety of tools to pry and pull and eventually got it free.

Thanks for the tips and advice. I was thinking of giving up and had been considering not replacing it if I couldn't get it off, even though I could see and feel some grooves worn in it. Now this motor should be leak free when I get it in the car.