As for no overdrive, what you might consider is to control that yourself.
You would have to make a small jumper harness that would attach to the three pin connector at the trans. Power to the center pin with key on, then the front pin is overdrive and the rear is lockup ground wires you would control from the cab.
Once in third gear you can ground either or both to control OD and/or lockup. If you consistently get them then your problem lies outside the trans.
I would try that first, sounds like you would have no problem making this harness.
A stuck brake switch will also prevent lockup.
Another quick test before you make that harness, take it for a ride and see if cruise control works all the time. If not, very good chance brake switch or PRNDL. One more item TPS. While they act up more on the diesel trucks they do act up on gas. You would have to monitor with an analog voltmeter, not digital. The needle should never jump around, it should move very smoothly. Idle around .65 and at WOT should be be around 3.5-4.0 if I recall correctly.
