The best way to check which engine you have is to look at the engine code that's etched into the block. It's located to the right of the exhaust manifold and is stamped vertically.
Here's some photos of it's location:
As you can see, mine says 5A as it has a 5A-FE engine. It will says 4A for the 4A-FE or 7A for the 7A-FE. You will have to get down low to see the numbers on the block and may have to give it a bit of a wipe to get rid of any dirt etc, but this is the most reliable way of checking which engine your car has.