1967 Barracuda - Slant Six (orig) or 440 Big Block? Daily Driver, Need MPG

like they say, buy a good running slant or let someone give ya one!!!!! you'll never get ya $$$ out of the rebuilt slant.unless you put 300,000 mi on it!??? keep the 440 for when you can afford it. or lke they say, pickup a cheap foreign made beater. and save the classic....
advice from the old, wise one!???????????? LOL