They never were arched up, they are designed to be flat. Here's what the 1937 Chevrolet Engineering manual says about front springs. This manual compares to old '36 chevrolets to the new and improved '37s.

" The front springs on the HALF TON truck are revised to make them of the "flat spring under design load" type, thus eliminating the camber and contributing to improved steering geometry by reducing to a minimum the "walk" (fore and aft motion) of attached parts. "

"The changes are confined to the first and second leaves of the spring. The rear eye is of the Berlin type, the horizontal centerline being approximately on the centerline of the first spring leaf. The second leaf is extended to wrap the new eye partially to give it stronger support. By this means, greater safety is made available in case the main leaf breaks near the rear eye. Additional improvement in the steering geometry is secured by reducing the slope of the spring."

Joe

1937 Chevrolet Inline-powered Streetrod