Here are the studs I found new in the box. They are slightly different but pretty much the same. I have not measured them yet but they appear to be what you need. One has H131 cast into the base and the other has KH M probably meaning Kelsey Hayes, they are both 7/16" left hand studs.

Left hand stud.jpgLeft hand stud 1.jpg
The funny thing about science is that if you change one miniscule parameter you change the entire outcome to the way you want it.

JB Rhinehart, Realist

A-Body's RULE!