whats it like to drive a 6-71?

> whats driving an old school blower like?

A lot of fun - as in perma-grin fun. Oh, and tuner drivers will not make eye contact.

> how will my gas mileage cruising on the highway

I don't have highway stats but around town I'd say I get as good or better mileage as I did with a single carb (850DP), normally aspirated BB. Crack the throttle and you're moving. Really depends on how heavy your right foot is.

> can I run pump gas at 93 octane

Yes, no problem, if you keep boost levels reasonable.

> The 440 is a tight fit and what about hot headers

Run the headers you want that will fit. The blower will definitely generate more under hood heat. I run a heat shield under my master cylinder. My floor boards get pretty warm. No problems though.