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:
U Bolt Eliminator Base Plate
Product Details
Brand: Welder Series
MPN: 15712
Thickness: 3/8"
Hole size: Outside holes 3/8", center hole 9/16"
Clamp plate base for u-bolt eliminator kit WS15710. Center hole is 9/16''. The 2 outer holes are 3/8''. 3/8'' steel. 3-1/2" x 4-3/8".