COPO 4.56 High Impact Gearset NOS? 3917973.
 

COPO high impact 4.56 gearset for 12 bolt. Tooth count 9-41. These look to be NOS but can't be 100% sure. GM box has part number 3917973 listed and box is dated 8/4/72. Pinion has part number 3916231 and is dated 1-73. Ring gear has part number of 3916230 and is dated 1-72. Box is almost destroyed since it got damp at some point. Gears have a few extremely small spots of pitting here and there since they were damp as well but will not cause any issues once installed. $350 shipped to your door or best offer for the set. Please message me with any questions.

-Matt

Re: COPO 4.56 High Impact Gearset NOS? 3917973.
 

$350 for the set if you're interested.