Heater Core/ Dashboard
Don't know for sure how these trucks are, I just hope its not like the early 80's Mustangs. The whole dash had to be removed to pull the AC plenum chamber out the get access to the heater core. NASTY!! Good luck. I hope Ford302V8 is right.
I am assuming you are not getting much heat, is this correct? If so you don't have to take out the heater core, there is a simple fix. It is probably plugged up with debris so just detach the inflow and outflow tubes in the engine compartment (near the water pump). Then just stick a hose in the outflow tube to free the debris and then the inflow tube. I had to do this during the winter and now my car gets real hot.
i still cant get to it with the glove box out. and i get heat it jus smells like coolant. and the coolant is now leaking out of the firewall under the truck. and lately it has been startig to smoke a little.
You've hijacked an 8 month old thread, suggest starting a new one for better exposure. Are the heater hoses the same temperature to the feel? They should be nearly the same temp and the top hose. If they are nearly the same temp, you probably have circulation. Then it could be the blend door. This door directs the air flow across the heater core or around it.

