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:
Upper Frame Plate for LS200
Product Details
Brand: Welder Series
MPN: LS210
Thickness: 3/16"
5-1/4" long x 4" at the large end.