Whats the Correct size wiper blades for '66 Dart?

As the title says, really.

I can't find the old wiper blades that I took off in Aug 2010 and have no idea what size is the correct one for my '66 Dart. Some websites say 12" some 13"s and some even suggested 15s!!

Im sure you guys here know better...

Cheers

Syed