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:
Batwing Side Plate for Hairpins
Product Details
Brand: Welder Series
MPN: 28905
Country/Region of Manufacture: Canada
Thickness: 3/8"
Hole size: 3/8"
For hairpin radius rods. 3/8" thick with 2 holes, 3/8" dia. on 4-3/4" centers. Priced individually.