i had to replace heater core ,put everything back together and now when i turn the truck off ,i cannot get the key out it will not flip all the way back.

 

Its probably not your problem but i'll mention it anyway. If you took your dash panel off at any point then check that it is all the way back in place. If it is not, it could be holding the shift lever from going all the way into park, and the key would not come out. Sorry i couldnt help more.