On the firebirds the alignment hole for the spring, and the spring pocket, are on the frame. The upper part of the spring is what needs to be lined up in the frame pocket, not in the arm.

If you still have coil clash when they are both lined up in the frame, you will need new coils.

The speed nuts might be available thru a catalog... I thought the bolt just screwed into the arm on these though? Anyway, when I run across a car with a stripped arm or broken speed nut, I just use a regular bolt/nut/ lockwasher combo. If not doing a 'correct' restore, it works.
If it has to be 'correct' you might need to heli-coil the arm, get a new arm... or find a speed nut through a catalog.

I dont remember speed nuts for the shocks on my Firebird, but I could be wrong.