for one thing, they're imitations of cars built with polygons.
The line in the spoiler of the second picture looks exactly like the split in the spoiler of a stock 98(?)RS spoiler.
The headlight shape in the first pic looks like the projection lights of the 98 as well. Remember that in NFSU, you can replace the headlights/tailights as well.
The taillights in the Second picture do wrap a bit around the side and come to a point, a classic Stealth/GT line. And, you're right about the hood length, but that [i]might[\i] be attributed to an imperfect render.
Anyway, I'm not saying you're wrong, just presenting my opinion and some of the reasons I have such an opinion
EDIT: Also, if it IS a 3000GT:
1)I've just become more interested in the game.
2)it better be the VR4, and
3)it better be one of the best cars in the game.