Salvation has always been - both before and after Calvary - by grace through faith in Christ. Those who lived prior to the cross looked forward with faith to the Messiah's substitutionary atonement, while we look backwards in time with faith to the cross.

Both groups of people, despite having been "chosen in Him before the foundation of the world (Eph 1:4)" were yet dead in their sins and unjustified until they believed (Heb 11:6).

-Robin