long thread here! no one has pointed out the obvious here, the center plate holding the springs has wear too. certainly thats gonna have some effect, chatter-noise-somthing was going on near the end. 38000 miles, and always chatter? from day one? anti chatter rods tight to the frame? they are a bugger when the threads are bad or if you dont have the right size tool to tighten them. its a ******* size, not a 3/8 square, and bigger than a quarter. i made a tool on the mill and it lasted one bolt and was junk-too soft. next one i had to weld the head to the frame to get the nut off, then grind of the weld to get the bolt out. now, i order grade 8 allen heads from fastenal. so, are your bolts tight? next, flywheel surface. i have used flywheels that sat out side for decades and cleaned them up with 80 grit on a sander. never had a problem, unless it was obvious once the surface was clean. next is the issue of the disk center hitting the bolts. its from ft wayne, we'd all like to say its good, but if you still have another disk laying around, i'd like to know the distance from the hub to the spring cage that was hitting the flywheel. it could be a bad part. not ruled out yet. i'd take a grinder to the bolts if the distance is correct. next, clutch chatter can also come from other worn out parts. u joint would be obvious, you are there now, worn spline? bad front drive shaft bearing or thrust washer?, sheared pin on the rear coupler? also, as mentioned, it would be easy to check the runout of the flywheel, on the car. many crank grinders do not face that off unless you ask them to check it. i am not the expert here just maybe brought up some other points. i know you do lots of miles, bless you for that, i drive the heck out of my cars too. love your travel photos, and hows the new dog doing without a car to ride in? best wishes, skip