engine size...

I have seen 500 c.i.d in caddys before

I have also seen 500's in Cadillac, also Oldsmoblie had 455 c.i.

im lokin at a 872 racing hemi for my car but it is not production

The biggest capacity production car would have to be made in Europe in the 1920s or earlier. The Benz "Blitzen Benz" was a four cylinder with 100 horsepower from around 20 litres before WW1, and from memory some racing Fiats were over 24 litres (well clear of 1400 cubic inches). These cars could be ordered with touring bodies and were road legal at the time, the "Blitzen Benz" was even used as a staff car for some German officers in WW1! One of the recommended service procedures was for the mechanic to put his hand through the intake port in order to remove the exhaust valve!

As far as the largest engine to be put into a production car, it would have to be the 2008 Viper at 511ci. Before that is was the 1970 Cadillac Elderado at 500ci. The previous fellow, mentioned the Mercedes from back in the day, but those were specially designed race cars.

http://en.wikipedia.org/wiki/List_of_automotive_superlatives#Engine_displacement