reg cab/ex cab doors?

I'm needing a new door for my truck. I've been phoneing around for the door, and am being asked repeatedly weather it's for a regular or extended cab. I thought they were the same but the guy at the junkyard said there are two different numbers in the computer for them. Whats the difference? He thought it might be the bottom rear corner shape. Anyone know for sure?

there the same

doors are the same