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:
Reinforcing Plate
Product Details
Brand: Welder Series
MPN: 21192A
Thickness: 1/4"
Hole size: 5/8"
Used with the frame brackets in Model A rear four link kits. Laser cut 1/4" steel with two 5/8" holes on 5-1/2" centers.
Available for 1-3/8" OD bushings and 1-5/8" OD bushings.