318 and 360 gas milage question

I get 14-15 mpg in around town driving of my 68 Barracuda with a ~370 HP 360, A833OD and 3.55 gears.
In comparison;
The same car but with a \6 with headers, cam, 4bbl got 18-19 around town and 23 mpg on the hiway.
My 99 Dakota pickup with a 175 HP 3.9l v6 gets 17-18 mpg under the same conditions as the 360. The Dakota has never seen 20 and may get just over 19 on the Hiway.

The Barracuda has not been on a hiway trip of enough length to use a whole tank of gas so I have no hiway numbers.