I agree 360 or even 318 especially magnum's be a better option but even 273 has more potential than a /6, +48 cid, 2 more intake ports plus better heads, and even better heads are available, especially if your after street able 300 hp.
Not knocking the /6 I think it's kewl little motor when built up but more of a labour of love then a practical choice, especially at 300 hp, I doubt most of them even make 225 hp.