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:
Batwing Boss
Product Details
Brand: Welder Series
MPN: 10036
Country/Region of Manufacture: Canada
Thickness: 5/8"
Diameter: 1-3/8"
Hole size: 11/16"
Designed for front 4-link and hairpin batwing brackets.
1-3/8″ OD x 11/16″ ID x 5/8″ thick. The ID is tapered for Ford and aftermarket (Super Bell, Magnum, Deuce Factory, etc.) spring perches and for aftermarket lower shock mounts.