cam choice.....

This is a new build. I don't have the cam yet. I'm trying to figure out the best cam for my existing parts. I used to run a stock lower end in my 68 satellite with the .484/ .284 cam, a stock 340 intake and mild pocket porting and gasket matching. That car went 13.02 with no converter and a 3.23 gear. So from the sound of it the .484 is the best bet to run.
In reference to "install it at 100" can someone explain that to me?