Not the heater core I am looking to repair----already have that.
My issue is mainly sealing the box to the cowl where the air enters the heater.
Falcons used a big 'dryer hose' type seal-----Mustang used use a foam type seal.
The Falcon seal I cannot find at the Falcon suppliers-----the piece for the mustang is readily available.
I did find out that the heater boxes (the big fiberglass box) is the same from 60 to 65 in the Falcon-----65-66 Mustang----difference being the late 65 and the 66 cars had a hole cut in the box for a blower resistor for the 'new' 3 spd blower.
The heat/defrost plenum is a bit different, but I do not think there would be any issue with using one from an earlier Falcon or the Mustang.
I will find out very soon.
While in Atlanta this week, I visited Mustangs Unlimited and bought the heat/defrost plenum and a seal kit.
I intend on fixing my heater this weekend (dropping to the mid 30s overnight this week).
I'll keep all you early Falcon people posted