2956 Prewar Scale hopper with tinplate trucks advice

Doing as you describe will work (obviously). They have a tab top and bottom, if you remove the wheels, you can get at the tabs.  Ideally you want to remove them with the least amount of bending or force. You can see them in the pic below.  I usually pry the tab slightly and wiggle them out.  This keeps from smashing or scratching them which could happen by doing it the way you did. 

Its the tabs you have to worry about breaking off, not the slots btw. This is why you should minimize the bending effort, force, etc.

Either way works in the end.

I straighten one tab just enough to get the cap off. 

Thanks guys!
But I am afraid that I wasn't clear about what I need to do.
I need to remove the little metal clips that hold on the hopper doors on the bottom of the car. Lionel called them bearing caps.

these? if so I don't know, I don't have one to look at in person. sorry.

Thanks Dave!

The part you circled is a triangular cam. There is a spring underneath to hold the door open or closed.
I've circled a couple of the "bearing caps" in yellow.

Update:

I removed the door retainers (bearing caps) by grabbing them with a needle nosed vise grips (the jaws are smooth where they grasped the part), and pulling straight up while rocking very gently.

I am ready to reassemble the car now.
I am thinking I will just gently tap them back in place.
If they won't stay, I probably will put a very small amount of Loctite in the slot before installing the bearing caps. Don't want the Loctite to show.

Below are a couple of photos of the hopper door and bearing caps.