Dynamically resize fancybox popup window

[dr.pepper]

I've got an index.php page which then opens cars.php in a popup window using fancybox. However, the popup window is always too big for the content which is within it. I've googled it and assumed autoscale or autoDimensions would do the trick but unfortunately not. The content within cars.php can change depending on what I click on within index.php, therefore I can't set a static height and width.

 

Is there any other way of doing it?

 

cars.php contains a head and body tag which contains multiple images and some text.