I find engines with all kinds of bolts and plugs in the hole you mention and some of them are there to hold the pump when the spring on the bottom of the pump is gone or broken. Make sure the pump is not pinned with some bolt there or you will need a new pump if you break it trying to defeat this "farmer fix".There is a tool that holds the pump in place when you remove the pan....
You can see it in the lower center on the hump...
Make sure it's not in there!
There should be a short slotted plug there