Ranger Gears with 35s

Hey I have a 2000 ranger 4x4 3.0 v6 auto trans, and Im about to get a 7in lift with 35s. How bad will this hurt my gas and milage? Will a high gear ratio like a 4:56 be a necessity? Also will these mods negitivly effect anything else on the truck?

i have the same trk with 33's and the stock 4.10 ratio. you loose a little power turning the bigger wheels but i have had no problems in 4 yrs.