I seem to remember from my car audio days that the 4x10 was a GM thing. I would bet it's a 5x7. I'll crawl up under my wagon's dash tomorrow and see if there's anything remotely resembling a factory speaker.
Well, grim might be right. It all depends on where I measure from. I always thought you measured from the mounting holes. If you measure it from end to end and side to side, it's certainly closer to 6x9.
