So you DID replace the thermostat??? If not, have you tried to remove the thermostat but LEAVE IT OUT? This will tell you if the thermostat in there is bad, but might make for a useless heater--it will always run cold
.
I'm not sure why you replaced starter and "ignition box" (one would have to assume you meant the starter relay possibly?). Could you please clarify the part:
"Read everthing from water pump,radiator plugged and water pump impellers bad"
You said you want to get it fixed "first time around" -- sounds like that possibility is already gone
How does the radiator fluid/coolant look? Can it be drained via the pitcock at bottom of radiator?
Clarifications aside, me thinks if you were able to start and run it fine, I wouldn't initially suspect an electrical problem. That is unless something is dripping from one of the hose on a wiring harness or the like.
I'd rule out timing if you say it already starts. Does it run rough when it DOES start?
Some other questions:
Check the dipstick for oil level--any water drops appear there?
What is the temperature when it won't start? Is it boiling over?
Or temp at the "overheating" point"?
Does it start up again after it cools down?
Is there any visible water leaking?
Is the radiator full? (start engine FIRST, place heater in full-hot, THEN fill radiator)
That gives you a few things to ponder and hopefully get back to the forum. The folks are great at answering/guessing if you're good at explaing the symptoms. Sorry to throw so many questions at ya, but I think we all could help more if there were some other symptomatic correlations that might be made.
WHOBUB
F-250 overheating and Start Prob. 
Hybrid Mode
