Having started this thread and asked for suggestions, I need to follow up. With no access to a plasma cutter or welding torch out here in the sticks, I started in today with a cutoff wheel on the grinder, chopped off the welded-on rear shock mounts, and ground off the welds with a grinder disc. It was tedious work, especially because I had to be careful not to cut into the axle trumpets.
Next up, I will fab up a plate to mount to the braking plate flanges to check with a trammel for any variation in the distance between as a test for distortion caused by the previous welding job. So far so good and thanks to all for the suggestions.