Well, not much input, but from what I gather the 273 heads flow as good if not better than these (and 302 heads), same valve sizes, and are closed chamber 57cc so I'm going for it. Luckily the guy I sold my 273 heads to is going to sell them back to me. I think this will be a nice setup. I'll report back in a few weeks once it's running again and hopefully I'll also have the carb tuned and have dyno numbers.