I have the feeling there is a lot of confusion here between the beam bushes and the bushes on the arms. For the arms the best option is to fit the original type bearings from GGR.
But for the beam (the big mushroom type bushes) it is quite unclear what would be best. At least I wouldn't expect that the original rubber bushes are the best option here. Personally I don't see anything wrong with a poly bush for the beam.