Speaking of the Corvette, here's a thread about it! Wow.
Here's another video of the C8 GT3-R during the Sebring test a month ago, this time being benchmarked against the GTE car which is still racing this year. The two cars sound different with the GT3 car having a slightly higher pitched exhaust. I'm not sure what in the rules would cause this. Speed difference seems negligible but it also seems like the GTE car catches up over the course of several laps.
We can also see (and hear) the Garage 56 NASCAR testing. It looks to have slower corner speeds than the GT cars but noticably quicker acceleration. And what a considerably noise coming out of that thing, damn. It'll be amazing at Le Mans.
Here's Jordan Taylor himself breaking down some of the action.
God bless GM for continuing to develop their V8.