Need help, advice with my 318 build

The age of the engine has nothing to do with why camshafts are ground on an advance. The reason is very simple People always tend to overcam an engine. So, to compensate for that, grinders through the years have learned to grind 4* advanced in the hopes of picking up some of that bottom end torque lost to an otherwise poor camshaft choice.

Also, there is no set in stone amount of advance. Some grind 4*, some 3*, some 6* and some none at all. That's why it's always best to put the wheel on it.