Per the recommendation of another member on here (I believe it was Cab Burge), I am running Federal Mogul/Sealed Power 4094M's. They're a narrow, fully grooved, tri-metal main bearing. The only downside I can think of is if you want a bearing with the larger thrust flange for the later blocks, which the 4094M bearings lack.

I also wouldn't hesitate to use a set of King bearings. I don't think you can get the XP series for low-deck mains, but you should be able to get an HP series bearing.