Would like to get my 66 Cuda's MPG high to drive Nor Ca to So cal

hi I'd like to be able to drive my 1966 Barracuda, 225 slant six auto 3 speed to Los Angeeles, 9 hours south from where I live, either once a week or once every two weeks... I had a 1966 Dodge D100 that made it down and back with the same engine, but manual, in 8 hours each way. Is this possible, can I make it be able to, with good gas mileage on the cheap side, or it this asking a lot? Too much of a long haul? It's got 13 in wheels, a one barrel Holley Carb, and an in accurate gas sending unit hehe

Of course, the cheaper the better. Any info, advice or cheap parts for sale, I'd be interested in! Please private messages me, would be more simple for me. Thank you!

Hayley, Cuda chick

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