I wanted to give you an update. Your suggestions helped.
After reading your suggestion, I went back and looked at a few things. The air flow at the registers just wasn't what I thought it should be. Remembering how much I had cleaned out of the heat chamber, I looked at the blower.
I pulled the blower, took it apart and cleaned what I am sure was about 2 lbs of dirt and dust from the blades and housing, blew as much out of the motor as I could then reassembled everything and reinstalled the blower. the heat exchanger looked go- no cracks, or openings that I could detect.
I also pulled the burner, and used canned air to clean soot from the pilot light and burner and used a small wire brush to clean the thermocouple as much as I could. I don't think this unit has ever been cleaned.
I turned the thermonstat up to about 90 and tested the temperatures with a wireless indoor outdoor thermometer (Pretty handy for that purpose). I now get 72 intake and 85 at the register.
But I don't think it is running as long as it should be. Once the burner lights and warms up, the blower runs for about 2 and a half to 3 minutes, then stops. But, I can hear the burner still going. It warms up for a bout two more minutes, then cycles again. The burner runs the entire time. So it is "keeping up" with the temperature, but not getting ahead of it, so to speak.
I tried adjusting the anticipator on the thermostat, but I can't see that much difference.
Should I replace the thermocouple? Would that help?