I think we are over thinking this repair.
First the dent is accessible very close to the large air horn opening.
You can make a simple tool out of a old leaf spring. You need to fashion a flat spoon shape on the end of the spring leaf. Figure out how far back from the opening you require, heat up the spring with a torch and bend a 90 degree bend into the leaf.
You can use this new tool two different ways during the metal working process. Mount the spring in a vise and use it as a dolly inside the air cleaner. Or build a 2 by 4 and plywood fixture to hold the air cleaner upside down and use the new spoon dolly to work the dent through the air horn opening.
If you go the "welded stud" route, you will end up with a bunch of small raised dents. The new spoon dolly will help you work down these small dents.
The idea is to straighten the dent as simple as possible, without causing more work.
Just another thought,
John