Mad Horse, is it just me or have you been gone for a long time? Haven't seen you around here at MW for quite some time.
Anyway, you cannot make a valid extrapolation from only 2 points, that the majority of Fords lean to the left b/c your Thunderbird and Mustang did
. Have you checked the frame of your car in the front behind the front left fender, the area where your battery is? It could be rusted through. I am only saying this b/c the last '79 I owned lean to the right in the front and this was b/c it (the frame) had rusted through and broken apart so the front was kinda hanging/leaning. I've owned 4 Mustangs so far and only 1 of them has leaned.
Also, you may just have worn front springs.