Thanks to everyone who replied, on and off list, to my mower motor queries. Your kind assistance is much appreciated!
I designed a simple jig to pop the commutator end caps off the motors, and it worked on the first one I tried, although it did leave the bearing in the blind hole. I'll push it out with the hydraulic method. On the next one I'm going to hit the end cap with a heat gun which I think will make the bearing stay on the shaft.