I'm restoring one of my Avanti's. The factory shop manual says, It uses a 12 spring pressure plate with the 4 speed trans. Mine, which is all original has a 9 spring pressure plate. Later build, 63R 3186. I have heard there was some problems with the Z bracket welded to the frame with a 12 spring. Could they have changed them to 9 spring later on. I plan on putting in a 9 spring when I reassemble it. Not planning on Drag racing it. Was just curious.