Rearend info help

Explain please?
I'd drive it around town in second, and use high gear above 50mph on the highway.
A friend and I drove home from bowling after midnight one night, in his low 2. something geared 305 camaro. 20 freeway miles. Didn't realize that we were in second gear the whole way (350 turbo) till we got off the freeway, and got a harsh downshift to first. (And we WEREN'T drinking, just tired).