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:
Gusset, 8" x 8"
Product Details
Brand: Welder Series
MPN: C006
Thickness: 3/16"
Used in our #C005 Chevy motor mount kit.
Large angle is 90 degrees.