I should have replaced my door seals a decade ago.

Decided to work on my rattling doors and along with new strikers I replaced the door seal on the cab, as that's what locates the door.  5 minute job and it feels like a new truck, since the seals were completely gone on both doors.  It sounded like driving with the windows down at all times.  The driver side was a bit confusing, until I got to the passenger side and discovered there's supposed to be a lip on the floor too, which was rusted away completely on the driver side.  I just bent some stainless on the brake and riveted it in place, which probably brought to job total to 15 minutes.  If I haven't been clear, I highly recommend doing this.

Glad you got it figured out!
I'm sure the driving experience is a lot of more pleasant without the wind.

The upturned lip (which is really the pinch weld between rocker and cab floor) unfortunately traps water from the drivers wet or snowy boots. When the moisture makes into the carpet or padding under a rubber mat it hangs around forever, doing it's damage.

Yes, good weatherstripping makes a huge difference!  

Really it was less figuring it out and more deciding to care enough.  Now that I've moved my commute to work includes interstate, and I'm making a point to drive the truck at least once every other weekend so it doesn't sit too long.  It's never going to be a quiet ride as loud as the engine is but that at least sounds pleasant.

Much easier to heat or cool, depending on the season.

Glad you can still enjoy your truck!