(Coming in late to this discussion but wanted to chime in with some things I found out looking into the 3904362 I got from the dealer when I built the motor for my 67 Corvette back in the late 90's)
I was told at the time this was the new number for the 3863143 cam beginning in 1988 (66-69 427 Sp Hi Perf, and is a mechanical cam based on lifter application). My engine build notes say the 362 cam was identified 921559 on the end. An important difference is the NOS 3863143's I've seen all had grooved rear cam bearings. The 362 cams were all the later style without the groove.
3863143 Cam:
https://www.yenko.net/forum/showthread.php?p=1251981
https://www.yenko.net/forum/showthread.php?t=149138
https://store.tracyvette.com/item/1676/
3904362
https://www.ebay.com/itm/NOS-GM-Soli...-/333739856437