I installed the 4X4 calipers last year and also had trouble bleeding them. I had the same symptoms as you do. Hard pedal, no braking action.

The problem was I installed aftwermarket braided S/S lines from M/S. The lines were a bit longer than the stock rubber lines causing the lines to loop up from the mounting point and back down to the caliper. They were about 5-6 inches above the caliper and would not allow the air to flush out . I finally removed the cailpers, holding them above the SS brake line while bleeding and that did the trick.

Good luck

Too much snow, cant move the car into the garage tonight. Ill try again when its plowed better. And its so darn cold!!! Thats propane heater was my best investment in this project!