Never have heard of any in the form of a COPO but I do know a guy that ordered one and a dealer in N Illinois put a 427 in it for him with less than 150 miles on the org 396. Car later got wrecked (1971) and last I heard it was still in peices with the Org 396 next to it. Been trying top pick it up for sometime. One day it will be here i Hawaii
The 68 Daytona pace Car was a RS/SS with a 350 HP 396 in it.