Thanks to all for your time insight.
Not much time over this last weekend to do very much. I checked the bushings, alignment at bottom of steering shaft and did a little lubrication.
I took the truck out last night. No issues backing out of various parking spots on the short trip. Upon arrival home, when backing down the driveway into the garage, from time to time, I would move from reverse to neutral, just to check function. All was well, until the last maneuver. Inside the garage, cutting it tight to the wall, I was parked and ready to shut down. The lever stuck in reverse once again.
Then I recalled... the only instances where this problem occured was when the wheel was cranked hard, at low speed, one way or the other. Could there be some bending or flexing at these extremes that is interfering with the normal function of the linkage, as it is tied to the steering shaft?
I have a friend coming by later in the week to operate behind the wheel while the invetigation continues.
Thanks again!