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:
Front Four Link Frame Bracket Side Plate
Product Details
Brand: Welder Series
Thickness: 3/16"
Hole size: 1/2"
6-1/8" x 4-1/4" with 2 holes, 1/2" dia, on 4-3/4" centers.
Usually used on Ford Model A’s or full-fendered T’s. The upper hole is 3/4″ from the top edge. The lower hole is 5/8″ ahead of the upper hole.