id think the extra weight would kill the swap even if did fit. Youd probably end up with less mileage from working that little motor so hard. Why not try to work with what you got. Ive seen some decent numbers out of those cars.
start a gas log and a home page describing your car in the garage section. we can then point you to some tricks to try. also check out the 201 gas saving tips at the top header. some stuff is really easy to do but without a good gas log you dont know were you stand.