Looking for advice, BB headers vs. HP manifolds

Sounds like a good plan. My advice is to stroke the engine so it has more torque and is easier to drive around town. Use some high quality aluminum heads, Edelbrock or Trick Flow and put fuel injection on it. You'll also want to put a 26 inch radiator in it so plan ahead on cutting the core support so you can put a big radiator in it. I'd sell the Offy 360 intake and use the money to buy something more modern such as a Performer RPM. You might want to read the thread on my BB Duster. I covered a lot of the same things in my build that you're asking about: Starting a BB Duster project