Update:
Radiator was about 1 qt. low, and added coolant mix. Two 20 mile trips this weekend @ 50+ MPH, no problems. No visible signs of leakage.
This morning, 40 mile trip, ran fine, started getting warm after about 15 miles on thruway in wet snow, freezing rain, fans came on and cooled right down. Going to get new radiator cap anyway. After lunch steam coming from grill, but believe just water burning off from road-spray/wet conditions.