You should probably verify the PN with your application, however those look a lot like the ones used on military trucks. (See image)

The GMC PN for the kit is 608438. They come up on auction sites like e-pay quite frequently. There is actually a listing for some now. Just do a search for "GMC" and "608438".

Best Regards....
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Last edited by CrowbarBob; 09/19/2020 4:17 AM. Reason: Typo