For the yellow car, here is a collage of several:
http://i.imgur.com/55NeTG7.jpg
First one is a Facel-Véga, last one is a Cadillac (but now I see you say it is background, so it is not that... and you would have recognized it anyway :D)

edit: no need to split I suppose, this thread can be used for discussions about identification of comics cars.