I have not played guitar in a while, and my callouses have gone away. I have been trying to get them back with great success in my middle and ring fingers, well enough in my index, and barely any in my pinky finger.

What are some alternate chord fingerings that increase callous formation in the pinky and index finger?

Thank youuu!
Just play - callouses are just your fingertips toughening up. If you play til they start to get sore they'll toughen up. If they don't get sore then...why do you need them to be any tougher?