Well, unfortunately, I'm no closer to solving this mystery than when I started. I pulled the engine out of the truck last night and removed the clutch. The clutch disc is installed correctly! The raised face and springs are toward the pressure plate side. I misunderstood what was originally being said about the raised hub, because the flywheel side of the disc also has a small raised hub where the splines mate with the drive shaft. Anyway, I'm sure it's right. The pilot bearing also looks normal and the clutch disc slides freely onto the splines of the transmission shaft.
So, I'm not sure where this leaves me. I guess I will reattach the disc and pressure plate to the flywheel and try to bench test the clutch with the engine out of the truck. Obviously, the clutch disc needs to spin freely under these conditions. If it does, then the clutch is okay and the transmission shaft must be binding on the pilot bearing.
It's a good thing I enjoy this hobby and I don't do it for a living.
