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:
Support Bar
Product Details
Brand: Welder Series
MPN: 70006
Thickness: 3/16"
Hole size: 3/8"
5-3/8" x 7/8" with holes for 3/8" bolts (one is slotted). Designed for #WS70014 transmission mount kit.