When we ran a full service chassis fab/turn-key hot rod shop a number of years ago, it was always useful to have threaded things around to weld into the frame for some kind of mount, etc.
Here’s a list of all our threaded things for your reference:
Differential Plate, 8" Ford
Product Details
Brand: Welder Series
MPN: 20668D
Thickness: 3/16"
Hole size: 2 @ 3/8", 1 @ 1/2"
Used in our bolt-on rear 8" Ford Panhard kit. Grid in photo is 1″ square.