Stiffness is almost unrelated to the steel alloy, mild is 99% of 4130, it's the diameter that matters. 1" is popular so I guess it works. Thicker wall does very little compared to going up to 1-1/4".
As a restraint in tension only, I've used 5/32" steel wire braid with thimbles and lead U clamps, never moved, weighs nothing, costs nothing, silent, easily adjustable if needed. Also makes a nice vertical restraint to prevent ripping that driver's side rubber mount.