If you ask some of the old SS and Stock Elim racer, it was fairly routine to run the 2800# springs on heavier A body cars. 4 speed cars tended to like the softer spring rate.
The shocks are not stiffer. Most of the recommended shocks were generally truck or C body items. It's the length of the shock that matters, not how stiff. I had a saying, you can run junk springs or junk shocks, but not both.