Warning : You may know that this is a kit car, and it is known for using different V8 engine swaps according to the model type. I found that LS3 & LS7 (chevy engine) roughly sound the same, only some lexus v8 variants were sounding really different so I didn't link videos.
EXTERIOR SOUNDS :
https://www.youtube.com/watch?v=8P4OpBO73s4 -> Some accelerations (00:00 - 00:30 / 01:28 - 01:35). A fantastic clean startup sound at 00:50 !
https://www.youtube.com/watch?v=bLd33lgxQfU -> Close to exhaust revs (low - mid range) sounds neat. Might be useful.
https://www.youtube.com/watch?v=7gJRjMp2_OQ -> Drive off and acceleration. Rather to give an idea of how it sounds. Has a good rumble when shifting.
https://www.youtube.com/watch?v=-tSe6tLMOWs -> 00:00 - 01:00 -> Very nice accelerations, could also be used for exterior acceleration maybe. Some inboard sounds, but with gravel sounds unfortunately)
https://www.youtube.com/watch?v=4QzJW7Rtwd8 -> Acceleration, and a nice decelerating sound. Idle + revs.
EXHAUST SOUNDS :
https://www.youtube.com/watch?v=gyvb3cejuXw -> Idle, accelerating, decelerating. Close to pipes.
https://www.youtube.com/watch?v=JDsl2duk1CY -> Idle, slow acceleration, fast acceleration, decelerating.
https://www.youtube.com/watch?v=80n-AtVyG8o -> Could be useful for low range rpm sounds.
https://www.youtube.com/watch?v=78aptZjGn4E -> 02:06 - 02:40 : startup + two revs midrange.
INTERIOR SOUNDS :
https://www.youtube.com/watch?v=micLBqCq1Gs -> Nice beefy sounds. Clean accelerations & decelerations. At 03:57 a high rpm rev sound that could be used for a rev limiter sound?
https://www.youtube.com/user/spydrb8/search?query=ultima (channel) : the dude has inboards of his ultima, it has a LOT of action. I think you can get everything you need to make a full inboard ultima gtr sound.
https://www.youtube.com/watch?v=U0a9mTVo-W4 -> Another nice inboard, sounds more muffled, could be useful maybe.
https://www.youtube.com/watch?v=lvXW0r48Jr8 -> This one has a transmission sound. Sounds interesting too.
https://www.youtube.com/watch?v=zOVXXLWlEo0 -> Another clean inboard action
https://www.youtube.com/watch?v=tyP8D1C3AXU -> One of my FAVOURITE, I have the feeling that the engine is behind me. Loud, lovely !
https://www.youtube.com/watch?v=78aptZjGn4E -> has some constant rpm sounds with a view on the gauge. Could help.
CAR LINK :
I'm using the ULTIMA GTR720, the best I've found so far. Correct limiter at 7k rpm. I'd recommend this one. (There is a 500hp one also in that link but the limiter is fucked up)
https://mega.nz/#!dJ1QHK6T!yfl4aw2e7kf-js9bczH0wMnsZ9g4IQSCWsA5MUJA_Wk
https://www.youtube.com/watch?v=KO2-3NLU1Ok -> How the car is and sounds.
I hope this can help. Also If there a things you miss as samples you can tell me I can try to look closer for it if you can't design it or use samples from another car mod / source.