Currently rebuilding the entire front suspension on our 66 2dr hardtop. After some looking online it seems the build date is a factor when ordering. So I went to my local parts store and ordered a bunch of Moog then asked about springs. The build date came up again. Ours is a January build and the change is sometime in February. I asked my parts guy what the difference in the springs were and all he could see was that the early build was 1 inch taller at 18 inch iirc, the later at 17 inch. Everything else looked the same. Does anyone know why this is? Did they just lower the front and inch in February?