The stamp set I am using is Retired (Long ago!) by Stampin' Up!
To make your lines evenly apart make incremental marks at the top, bottom & sides of your paper and line up with the stamp lines on the imaging sheet. Once your first lines are in they become your guide to the next stamping lines. If you need to extend the size beyond the size of your stamps the best way to keep there from being a line across your finished work is to stagger up & down your original lines so that the stamped connection is scattered through your piece.