the temperature gauge slowly moves to red while riding a longer distance (parkway etc). When the heat is put on full the needle will slowly go back to middle. A new radiator was put in but it’s still a problem. Ford dealer says a leak but my mechanic does see any.
Are you loosing coolant? If so then a leak is a possibility.
If not, the problem is elsewhere.
Is the parkway a low speed zone? Possible your fan is not switching on.
Assuming the radiator is the correct one for this car, I agree with looking at the fan next.
Keep in mind that you want to solve this as quickly as possible. Overheating a car repeatedly or severely can cause serious damage.
Was the old radiator corroded?
Has coolant been changed on the recommended schedule (typ. 5-7 years)?
Has the head gasket been checked for leakage?
Could be bad thermostat. Check to see if your oil looks OK and no antifreeze in it. Not much to these cars. Check the low speed fan relay. Its in your fuse box inside the engine compartment. or the fan resister its against the fan housing.
Was this ever fixed?