most stock front Chevy springs sit flat when loaded (negative arch when worn). So I'm thinking when those are loaded they will sit 4-5 inches positive arch. My guess is that they are 4-4.5" lift springs but will probably give 6" lift if you currently have old worn out stockers on it now.
Just a side note....... those look like old Ranchos or Superlift springs (square cut, non tapered, and no Teflon between springs) so they will probably be annoyingly stiff.
Chris