My wiring schematic shows a single horn for a 72.
didn't they have two? Low & High note?

My 72 only has one horn...about to replace it...sounds whimpy

My 72 only has one also.

Both my Chevelles have dual horns, but I am pretty sure it was an option.

Are they both the same pitch or is one a high tone and the other a low?

My 71 --307 Nomad wagon came with one horn. I installed a pair of 70s High & Low.
Bob

I believe dual horns always meant two pitches. I don't for sure about Chevelles, but lots of GM cars were dual pitch. Look at the horns, you will see the note stamped.

There seems to be two push on connectors. Does the single horn have two terminals?

Usually only one connector for each horn.
I would guess that all of the cars had the wiring and connector for lo/hi horn even if it was an option.

Geeze my old Dodge pu has only the hi note---hate it.
I've not seen many cars with only one horn since----ever

There seems to be two push on connectors. Does the single horn have two terminals?

My 72 had 1 horn. One of the connectors is power the other might be ground.

OK thanks for the help on the horns. As i traced back the wire it is a single power lead split to two terminals so mine must have been setup for dual horns.
On another note, I have no instrument panel lights at all. No directional indicator lamps although all the blinkers work.
I changed the fuses and all seems OK there.
Any thoughts? I thinks its weird that nothing on the dash works.