The Google Nexus 7 fits like a glove in the double DIN opening. A mini Ipad would need some minor trimming, bondo, sanding and painting. But doable.
Car audio is all about creativity and not so much does it fit.
Perhaps search the car audio forum as that would have been the better place to start. I'd recommend you find the nexus thread to see what that guy did to put a tablet in the dash and look pretty OEM to boot.