I have always screwed in a sheet metal screw to opposite sides of the metal part of the seal and use a slide hammer to pull it.
I was thinking this yesterday, weld up some way to attach to the screws, use largest screws possible.
Another vote for the screws method - works well. If you spray some freeze-spray on the seal, it'll shrink it just a tad. Any advantage you can get will help
Or you can jack up motor and remove support to take out 3 bolts on trunnion and change seal on bench.
Bob