If you don't want to damage the axles, you really should just take the axles to a machine shop and have the old bearings pressed off. Trying to cut the old bracket off is a recipe for disaster. One slip and you've got a damaged axle.

A torch would most likely overheat the axle and/or bearing.

A cut off wheel will be difficult to work in that tight space without getting into either the bearing or axle or both.

The axles are worth more than the bearings. I wouldn't take a chance with them.