There are a few header manufacturers out there that make cast iron headers. While they don't flow quite as well as tubular headers, they still flow a lot better than iron log manifolds, and they seal as well as the manifolds. So I don't think you will have leaks.
Splitting the manifold will have advantages similar to the smooth sweep Fentons but would be just a little shy of the Fentons power making. And I'm sure uncorking the exhaust with a dual exhaust will go a long way to adding power and torque.
For mine, I would like to get a pair of Fentons, run dual exhaust exiting out the sides in front of each rear tire, and a pair of Superturbo mufflers. I like the silence at cruising speed and the aggressive tone at WOT.
And if I change the exhaust, then I'll want to change the intake and use a modern 350 cfm Holley 2-barrel.
It's the "while you're at its" that will make this pricey for me. I guess I'll just collect the stuff and do it when I have it all.
