Report "2 ton 305 engine...truck overheated..let cool down and replace water...continued driving and noticed temp was getting hot again..turned on heater and was blowing cool air...let engine cool down again and replaced thermostat...refilled with water and replace radi. cap.. engine would start but rough and just die...replace spark plugs and now engine will stay running at idle...took it around block and its like it has no power...real slow take off... and at idle if you turn on ac motor will die...checked oil and no water in oil...and no water leaks any where...and suggestions on what it could be?"