If you have a 103" now I don't know that I would waste the coin on a 107". Take the money you would spend on the 107" and put it into some work on the heads and add some cams.
You shouldn't see much difference in fuel economy. The motor will run hotter. I would add an oil cooler if you don't already have one.
Agreed!!!!!!!! a set of heads and bump that compression and pick a nice cam. and you will be good to go. Get a set of FM's heads and the TW555 cams.