I go 75 in front with minimum of 45-50 in rear unloaded. If I go lower or higher than that in the rear, I get uneven tread wear.I've settled on 80 in the front (I tend to go fast through corners) and 40 in the rear when empty.
That's with a truck bed and tool boxes, by the way, some 9,300 lbs. total.
When towing, which is almost always, I inflate the rears to match the weight.