First off; this is NOT a blue print. Just a little helper info for those who wish to do this on their shifter. Some additional pointers provided.
1) After getting and installing the tension stud, I really think it is a 5/16 X 28 thread. You can get those studs with a little plastic spot on it to keep it from rattling out. However, since I already had the 1/4 X 20 one, I found that if you correctly place the hole you are going to put in, you can also put a 1/4 X 20 nut on to lock it down.
2) Look close in the photo. There is a pencil mark to show you where the ball from the tension stud will ride.
Fabrication is often personal, so bear with me here. I used a 2" wide by 1/8" thick piece of flat plate. I cut one end at a slight angle to follow the Fomoco shifter mounting metal. I did this so I could put in additional welds to hold the plate in place.
I do think the width in the earlier photos shows that plate is only 1/2" wide. You can make your plate that way too for a more correct modification. I wish the photos provided in the article would have shown that.
I laid the plate I made over a 1/2" wide piece of flat stock. You can see the curve (to hug the factory steel bushing) that is required either way, now that the shifter assembly is apart. That hole is 1 5/16ths in diameter. Your choice - wide or narrow.
3) I did not add the additional plate up in the shifter detent area. Instead, I filed a depression in the plate so you would have to push in the shifter knob to get the shifter out of neutral. It is just a little notch.