I was looking under the front of my fb and saw that there was a gap between the vertical plate and horizontal plate on the control arm (I think that's what it's called). Here's some pictures and just how bad is this?

 

Has it been welded?

Scrap some of the corrosion off. Then you'll get a better look at the integrity of the metal.

 

clean it up and see if it's actually a crack, if so just throw them and find a good one.
It's not worth repairing IMO with plenty of arms around the place.