I just replaced the heater core in my 86 F-150 302 EFI and it took me about 30 minutes from start to finish and the core was ony 18 dollars at Advance. Just remove the glove box and you will see the cover right behind it in which you will find the core. Remove the cover. The heater hoses in the engine compartment will not lose much fluid if you keep the hoses higher than the rest of the engine.