Unported head quickness?

1972 duster 340, jerico trans, 5.57 gears, 9zx 30 slicks, stock unported heads, 1.88 & 1.60 valves, stock intake & T.Q. carb, 11.37 @ 115.50 mph, 1.49 60 ft, 3335 wgt

mission raceway, 11.21 @ 117.24 3335 wgt