Damper Dudes, 5509 Cedars Rd #2, Redding, CA 96001, 1-800-413-2673 is a great place to get your original damper rebuilt just right. They did one for my '69 428CJ, and I've got one for a '66 410 I need to take up to them.

For the CJ, I didn't have a decent core, so they provided one for me. Just my nickel's worth, but I'll use them for the F100 and the '57 Delray.