Most clubs do shoot stages that require 2 revolvers.
It is easier if both pistols and rifle are the same caliber. You only have to have one type of ammo that way and you don't have to worry about loading the wrong ones.
Shooting the Blackhawk does put you in the Modern class. There is a higher percentage of shooters in the traditional class. The number of Modern shooters varies from club to club. To give you some idea, the last match I shot had 76 shooters. 35 shot in the traditional class and 7 in the modern class.