Turbo /6 or v8

I'm debating whether I want to go with a tubo /6 or my 318 that I'd currently in my 75 dart sport. Im looking for power I've seen videos of 11 second /6s. My question is how expensive and how much would I have to do to the engine inorder to turbo it and get somewhat of a nice street car for friday night fights?
I'm not looking to be super fast just quick enough to compete with some v8s and turbo imports.