Most brands have an "endurance" pad version of bibshorts, and I would recommend looking for something that provides a degree of muscle support rather than flimsy lycra. It will cost much more than entry level bibshorts but will be worth it.
As for brands, I have found that Assos, Champion (clubkit), and Endura all suit me - DHB have decent enough pads but I have never found their "support" to be favourable to longer distances. Others I have heard which receive favourable comment are Castelli but I've never owned a pair.