Hi Allan,
I made mention in a post years ago about this mod but I wouldn't go so far as to say that was a popular mod. The hangers on the FGs are very strong and hardly likely to ever fail. Maybe the thread was called " FG Fleet Mechanic" .......man, that was a long time ago.
They made of pressed and welded plate steel. The earlier 2wd FEs have cast steel rear hangers. Some of the guys who run continually on the beach replace the original rear hangers with the cast ones because they last longer in the corrosive environment......... We are talking severe rust here. If I remember correctly I also stressed in that original thread that the particular environment that those guys run is the epitomy of extreme and that for 99.9% of serious travellers, the original hangers are more than adequate.
Regards
John