06 LLY code engine is still an LBZ with LBZ pistons.
1200ft lbs seems to be max on lb7-lly rods and 1300ft lbs max on lbz-lmm. this does not take into account for the one weak rod your truck may have or slightly weaker rods compared to the next set.
I think I would be really happy with 1000ft lbs honestly. If I could keep it cool and egt's down i typically run 2200-2400 rpm when on the freeway.