I know you are in texas, and the weather isn't as much an issue as it is up here... but you'd be amazed at how much it kills the MPG to idle the engine for 20 min in the morning to warm it up.
Assuming that isn't the problem... check the basics as mentioned already. Tire pressure, plugs wires, cap and rotor... how old are they? If you have points, then inspect them (or say screw it and convert it to HEI) Look at the air filter, clean the carb, yadda yadda yadda.
If you are like me and are too lazy to pull the 2500 pounds of junk in the bed... that'll hurt your MPG too. I have a whole front cross member in mine, frim rotor to rotor, plus a set of cement steps that we tore apart off the back portch... puttin a good squat on the 'ole girl. I KNOW it ain't helping my situation... but, I have no place to dump it.
You don't need some concrete chunks do you?
