Brake light switch???

I had a 69 Dart and the brake light switch bracket was adjustable. When you say your original is "snap-in type", that is what I remember. It is a round plastic tube which snaps into the bracket. You don't adjust that. What you do adjust is where the bracket bolts to the pedal bracket. There is a slotted hole. Crawl under and look again. Loosen the bolt on the bracket and slide it towards the pedal.

Unlike new cars, the whole switch is exposed and easy to see how it works. Almost the same as your door jamb light switches, except those short to gnd and the brake-switch switches the hot side.