Hi Ian
Do you need a switch, most of the Chevy parts have them around $20 - $ 30 dollars US.
Picture shown is the NAPA ECH ST11 which list for $54 and sells for $32. Also found them on
http://www.obschevy.com/ for $19.95.
The same switch was used on a lot of GM cars and trucks from 1931-1956
Cheers Phil