Same thing is happening to me, but with a twist
I have been having the same problems with my 1995 f150 4x4. The odometer stops working, the speedometer stops working, and the O/D light flashes.
but here is my twist. I noticed a while back (when the speedo and odo worked) that if I turned on my interior lights the odo, speedo stopped working and the O/D light blinked. Even opening the glove compartment would kill it!
I then realized that when I open my door with no key in the ignition that the interior lights did not come on!
My one uncle thinks it has something to do with the module that would dim the interior lights after a few seconds.
To me it definately appears to be wiring issue.