Ford puts 5W50 in the newer GT500s. 5W20 is a mileage-oil. It is intended to reduce pumping losses to help boost efficiency and fuel economy.
I don't think the modular engine's tolerances are so tight that it can't run a heavier oil. I've read that the HLAs (hydraulic lash adjusters or "hydraulic lifters") might pump up at very high RPM with heavier oils. I think 10W30 would be fine, even in winter. I've got 5W40 in my SC 2V and its fine with it.
Having said that, an engine with 194K miles has led a very long life indeed. If it's not making noise its bearing clearances are probably still within spec. You can probably still see honing marks on the cylinder walls... Whatever oil has been run in it has served it well. Changing to a heavier grade of oil to try to reduce oil consumption is only pushing out the inevitable. If the valve guides are sloppy or the seals are cooked then heavier oil is a mask. And 10W30 isn't exactly "heavy" so it won't really change the oil smoking a lot.
What are your intentions for the car? To keep it for another five years? If a basic compression and/or leakdown test were done and the motor turned out to be "tired", what would you do? Would you consider, say, a PI-swap with a used PI engine from a Crown Vic or Mustang?