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:
Vega Steering Mount Main Plate
Product Details
Brand: Welder Series
MPN: 20724
Country/Region of Manufacture: Canada
Thickness: 3/16"
Hole size: Bottom holes 7/16"
As used in the Vega/ GM 525 steering box mount kit.