Seeking 318 rebuild advice
I'm going to wager a guess because he already has the 318...the magnum--even the core--adds cost, and does require some different parts. I did the magnum swap because I acquired the long block for free from a friend...but I still had to buy parts and deal with some frustrations.
That being said, I can't disagree with your suggestion...lord knows those engines are everywhere, and a running 5.9 core shouldn't set you back more than a grand unless your local salvage yards are thieves.