If you're talking about the 2WD dual piston mod, mine dragged... the GM bearings had 18k miles on them from the truck it came off. I installed new hawk pads, put about 2500 miles on the car, drag never changed and was consistent both sides. Changed master cylinders at one point too (unrelated issue). You'd spin the front and maybe get a half turn at best before it stopped.
I did the C6 front conversion, used the same hubs/bearings, hawk pads again, significantly less drag.... I can get a turn or two out of them now even with brand new pads. My guess is caliper design... other people have complained of the same drag issue. Raybestos does make a generic "anti-drag" clip you can add to some calipers (believe I've seen it marketed for Ford calipers)... you could check to see if it fits. If I stuck with the Blazer brakes I would have looked into that next.