Good job, Turbo!!
Basically you want a bigger hole in the front of the 'T' so you have better access to the steering wheel u-joint. You're probably not like me and probably won't end up essentially rebuilding your car several times but if you need to get at the steering u-joint even once, you'll be thankful for better access.
I don't know if they make what I've always called "chassis punches" in the size you would want but I found this on the inerwebs (
https://www.trick-tools.com/Flare_Tools_78?view_all). I searched for "sheet metal hole flare tools" (without the quotes) because "chassis punch" just gave hole punches so I apparently don't know the real name for them! The flare should give you some extra strength to make up for the bigger hold. If that's not practical, you should be able to double up the area there.
Sorry I can't give you dimentions but if you experiment with positioning your hand at different angles in the existing hole, that might help you size your new hole.
Does that help?