The “overload” springs, above the usual leaf springs, were an aftermarket addition used typically on 1/2 ton trucks . These were, as far as I have been able to determine at least yet, not sold as a Chevrolet accessory. None are listed in the accessory catalog or master parts catalogs. I’ve seen these on some trucks used by farmers. My ‘46 Chevy 1/2 Ton had them too.
