What mileage does your slant six powered ride get?

In the fall 2016 I did a 5 week cross country trip (that included Route 66 ) from RI to California, part way up the Pacific Coast Highway then to Minnesota then home.
73 Dart with 1971 225, 2.76 rear, 904 trans, Holley 1920, points ignition, timing at 5 degrees, 205 75 14's. Car loaded with tools, parts, camping gear, survival gear etc.
Temps ranged from high 70's (southern portion) to 10 degrees (through Wyoming en route to Minnesota). Highway driving ranged from 55 to 70 mph. Lots of back road and city driving on Route 66 including 5 hours in LA traffic. Lots of hills and time spent at elevation car was not tuned for.
8,360 miles total. Average at the end of the trip was 19.7 mpg. Best reading was 21.9, worst was 13 in LA (lots of time idling then accelerating for an 1/8 mile to the next light so I could idle some more, accelerate, idle, repeat.)