[Redpiston]

Polishing up my emblems as best I can for their age and found that they were being held on by just a bunch of tape on the back side when I went to take them off. I noticed that none of them had any threading on them from previous speed nuts. Did they use barrel nuts originally? I looked up barrel nuts for 3/16 studs but the holes in the body don't seem to be large enough to allow it to go in the hole. On top of that the barrel seems to be too short for the stud on the emblem. I know that I will be taking the emblems back off in the future when I paint the car and I am concerned that I might break them trying to get them back off of the barrel nut. I bought some of the plastic speed nuts from Ames because that was what was used on the letters.

So the questions are:
Are these supposed to be installed with barrel nuts?
Can you use 3/16 speed nuts instead?
Can you use barrel nuts on the studs after you have used a speed nut on it?

[Deadhead]

If you have the studs, you are way ahead. A speednut cuts into the potmetal. This is really what you need, but also what you don't BC they can shear off the old pot metal. You might be better using some Goop or similar hard flexible adhesive in a plastic barrel nut. I have had the speed nut cut the stud off too short to be able to accept anything after, so I would not go that route.
If you are a nerd about authenticity, you can pry the tooth of the speed nut to make it less aggressive & hope for the best. Some Bonnevilles I have taken apart use a heavy weatherstrip type glue and the speed nut. May help lube it some & reduce risk of damage.