Sorry wkatt42 I have been real busy and frankly have not had time to get online much these last 2 days.
Yes, the heater core is generally located on the passenger side of the truck. Depending where the leak is it may spread to the drivers side but mor eunlikely this will happen.
Here is a picture of a typical heater core.
Ford Forums - Putts255's Album: Heater core - Picture