99 Suburban 2wd with 4:10 rear end?????

[72freak]

I am watching a 1999 Suburban 2500 2wd on ebay. I have been looking for a 97-99 2wd 2500 suburban with a 5.7 for some time. This truck is perfect for me but I am not sure about that 4:10 rear end. A broker has the truck so there is no information about gas mileage. I am wanting to stay about 17-20 mpg and I am not sure if that 4:10 will allow it. Anyone know?

If that 4:10 is going to to mess up my mileage can I just change out the ring and pinion to a 3:73 or something? Are there any computer changes that have to be made? Any sensors need changing?

Any information would be appreciated. I normally work on the older stuff so this newer truck has me baffled.