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:
Nutserts
Product Details
Brand: Welder Series
MPN: 965410
Available in 3/8-16 and 5/16-18, great for adding threads to finished surfaces, especially sheet metal up to 1/8". Priced individually. Also called rivnuts, or riv nuts.