318 cam selection?

Didnt really keep that close of tabs on mileage. I believe the original stock 318(2bbl) with 2.76?? gearing got 18-19mpg on the highway. With the other set up I drove the car from Albuquerque to here once and was around 15mpg. Was it worth the mileage decrease?? To us it was, and my son paid all the gas money for it while going to UNM for 4 years. Just the sound of the car through full exhaust and cheap turbo mufflers gave the impression it was more than what it was, Lots of questions if it was a 340. Now his mom is running a much stouter 360 in it in street class, we cant grow up!