what are the speaker sizes for an AP1 - both front and rear?

 

The front speaker size should be 6.5". You will need to keep an eye on the mounting depth of aftermarket speakers as there is the chance that they could interfere with your windows.

A good place to look for audio info is the link stickied at the top of Electronics forum:
https://www.s2ki.com/forums/index.php?showtopic=295344

The stickied link also references another site that shows measurements and install information:
http://users.rcn.com/dhintz/Michelle/Audio/audio.html

Hope this helps!