Why is my Gas Mileage so bad? '66 Skylark w/ 300.

is the inside of your tailpipes black? i think your carb is too fat at cruise
and i think your shift poinst are alittle late or need to use overdrive more
have the lockup alittle sooner . you could run a deeper gear and use the overdrive and still get the same or better mpg
my 65 with a st300(2 speed) gets more mpg than that unless i go over 65