Think I've found a stolen car? What to do?

[V3RSAC3]

I just dropped my brother around to his GF's house (because he lost his liscence), now she only lives around the corner from us. But on the way there down one of the side streets I see this absalutly beautiful Gunmetal Silver 67' Chevrolet Impala sitting up on a curb half in the grass half in the footpath. We slowed down to check out this beauty and it was so immaculate we creamed ourselves. ... On my way back I stopped to pay closer attention and I realised that the way it was parked that no owner of this would do that to such a car. I went around to the drivers door and saw that it wasn't closed properly. ... This all looks very suss and the street is very dark and no signs of households being awake...

I'm just wandering what you think I should do? Whether I should report this to the police if some guys pride and joy has been stolen he'll want to know where it is? or should I leave it incase, well im not too sure maybe the owner is staying in one of the houses? .. Sorry no pics it's so dark and cold and I don't carry a camera with me lol. Maybe when I go to pick him up I will get a snap.

What should I do? as this car is just suss.