What was GT2 and is now LMGTE, mandates 5.5 liters n/a or 4 liters boosted maximums. Of course there’s no maths for valves per cylinder and spy movies hear snail noises. So what does GM have to build a 4valve turbo motor upon? (The following is my wild speculation pointing at my good or awful Google Fu skills)
Lets begin with a Caddy 4.2 tt v8. I think they destroked it and boosted to Ferrari 488 power levels. That’s what I believe is plumbed into it. An engine from the caddy now run by an ex BMW head. Hmm...with all that golf club trunk space for turbines and intercoolers and secret sauce.
They could have run a stroker v6 based off an indycar, or their own high value 3.9 stuff but a turbo 6 Vette would be more sacriligeous than the Ford GT doing so and not sell anything. So look for a ttv8 street car running 650+ hp coming soon for the 2020 race season.