I also used Napa for a re-built steering box. I believe the one I got is 2 1/2 turns lock to lock. I just told the counter guy what I was putting it into and it was a simple bolt in (after getting the pitman arm off). Just remember to install the box before putting the pitman arm back on.
As for the distributor advance can hitting the manifold, there are multiple ways it can be installed. It is just finding a position that works and installing the wires in respect to that position.