couple question.. i have a 94 f150 with a 302.. single cab and a 8 foot bed.. i lidted it 4 inches and put 275/70 17's on it.. motor back duels.. now my gas mileage is 8 miles to the gallon.. im thinkin i have a low gear in it !! and wondering, how big of a gear can i put in the front and rear end to help the motor and trans spin them big ole tires !!!

and how do i know what gear i have in it ?