Just wondering what kind of fastener should be used on the plastic studs of the '72 "DART" front fender badges. I don't want to break those expen$ive pieces, and they don't look like trim adhesive was the intended mounting method. Is it a self-tapping nut of some kind?
thanks.

Yes, a tin self tapping nut.

Called "speed nuts".

I have some Swinger emblems and they have a push-on plastic/rubber sleeve on the studs instead of a spin on nut. Kinda like heat shrink tubing.

If you buy aftermarket emblems it comes with that stuff. I can tell you from experience they don't last long on a car...

One emblem I have is NOS and it has a couple of those rubber sleeves and they are hard as a rock. They'll have to be to cut them off with an x-acto knife.

The spin on nuts are better. Don't use the push-in inserts that go in from the outside. Major pain and can chip the paint if your not careful.

Push-in retainers are called barrel clips; they make nameplate removal easier but you have to size them correctly and they can be tricky to install.
The stamped thread-cutting nuts are fine if you can get to them on the backside.

I tried installed some Mustang emblems with the push-in clips and because the clear coat had filled the holes in too much they would not fit right. I should have filed the holes open with a jeweler's rat tail file, but didn't.

Thanks! Is there a particular size of speed nut that works best?

Also, one of my "DART"s is broken in half (between the DA and RT). Its pins have a very hard, yellowish plastic tube. I assume that's the "barrel clip" referred to above. And maybe why a previous owner broke it, too. Any way to fix that, such as soldering?

I think the plastic sleeves go on from behind like a nut would only they push on.

The other type of retainers that I had trouble with are like a funnel that go in the holes in the car and then the emblem pins go inside them afterwards. It's all supposed to fit nice and snug, but the hole sizes have to be right on or they don't work right.

You'll have to measure the studs and buy the nuts that are the right size. Ebay is full of them.

If your Dart emblem is broke just buy a new one. I think they are made of die cast pot metal?

Yeah... $63 worth of pot metal!

Too much.

I checked Mancini and they have them for $36 and change.

Thanks... didn't think to look there. $36.95 plus their "unable to determine shipping before processing order" might be more reasonable.