You can use a 0W-30 or 5W-30 without any problems. Most cars nowadays are using 20 weight oils for getting that last fraction of a MPG out of the EPA tests.

1967 Dodge Coronet Deluxe station wagon

1.03" T-bars, QA1 arms/rods, Cordoba/GM Metric/Volare brake & knuckle, XHDs, Hellwig rear sway, 318 Magnum w/ air gap, 727, 3.23s