Old Crow,
You don't really NEED an OAL gauge to properly load for the Ruger Number 1. For that matter, you don't need one to make accurate loads for bolt actions or any other actions either. The OAL guage simply makes it easier to determine that maximum length for reference. An inexpensive dial caliper does the same thing.
Simply start by loading the bullet out so that it touches the lands, and then seat bullet deeper in 0.010" increments and develope the load that is most accurate in your rifle. For most rifles/chamber throats, this means keeping the bullet ogive just short of touching the lands.
John