As it was posted in the original message: " Both of ours are based off of a 5.9 Magnum."
So I'm with @RustyRatRod that 6.7L encompasses multiple CID's
Using 408 would indeed be more accurate and a good argument I can use against him
I mean this guy is a fair bit younger than me so he's used to all metric callouts that are used on modern mopars and other brand-X's.
407 = 6.66L
408 = 6.68L
409 = 6.7
410 = 6.72