Max lift with stock valve length?

To tell the truth, I'm not sure if they are stock valves or not. I haven't pulled the heads apart yet, but it was sporting OEM lifters and orange/red stripe 340 springs on a original 340 lift cam. I do know that the motor was worked on at some point in it's life so anything is possible. I won't be running these heads for too very long or especially hard before I go to the next head/cam/intake configuration, but I really want to see how they do.