[cowmeat]

Need some expert advice here for possible MPG upgrade to the hooptie!

Black Widow has the stock 12" Festiva rims, so I've been considering a swap up to 13" rims ever since I have owned it. I've seen a lot of Festiva owners swapping up to 13" using the Aspire hardware, but I'm not sure doing so would benefit MPG or not. The Aspire rotors & calipers would be stouter, but would also add weight. I assume the difference in tire size would leave me with lower RPMs at higher speeds, but not sure if it would benefit MPG to do the swap. Also, would I need to do anything to make the speedo & odometer show correctly?
Would it make more sense to just swap to a taller fifth gear (if it's even possible in that car), or is there a different gearbox that would work for the Festiva? It doesn't have a tach, so I'm not sure what RPM it's hitting at 55 (my max speed), but I've seen that a lot of you guys swap fifth gears with Civics & Metros with good results.

If anybody can clue me in, I'd owe you one!