Here’s another early automotive cite — since “(big) honking” is used in reference to engines, it’s unlikely that it has anything to do with honking horns.
1973 Road Test (Mar.) “Changing Modes” in Charger Muscle Portfolio 1966-1974 (1995) p. 115: The engines which powered these cars were big honking monsters with names like the 426 hemi.
Thanks, Ben. That last cite is great.
I acknowledge the fact that people make the connection to honker, but so far there’s no evidence that “honking” was first used to describe noses.