Got me a new truck with a slant Six, what should I do?

Thanks, well this is my first slant six and I thought I would have some fun with it. I love the oddity factor this truck presents and I want to add to do a little more to the engine without swapping for a v8. Performance is a plus in this case without sacrificing fuel milage. My dads 64 valiant had a 4 barrel and headers with a 4 speed, and man that motor would scream haha. I like the 4 barrel setup but would it cost me fuel milage?