When I did my bushings, the metal didn't get red hot. It was just warm to the touch after about 2 minutes of cooling off after burning the bushings out. The hottest part of the flame (with a torch) is centered on the bushing itself, not the surounding metal. I would say, maybe 300 degrees is all the surounding metal is subjected to. Not to bad. Think about how hot a caliper bracket gets after some track time, haven't heard any horror stories with those. Certain metals react differently to heat. Think about what happens when you weld certain metals together, that is very hot! I can't remember much from physics back in high school, but today I would say that heat is a metals friend if used correctly and on the right metals. If any of my thinking is incorrect, someone please fill my cranium with the right info.
!M!