Fairly stock 318/904 w new gears

Hey guys I was wondering if anyone has any opinion of what this setup would be like. Ive got a fairly stock 1974 dart with the original 318 with just a 4bbl carb on it and some bigger valves. The torque converter is stock and so is the 904 transmission. Right now its got an 8 1/4 rear with 2.45 gears. Would there be a noticeable difference if i threw a 8 3/4 rear in it with say 3.91 gears? how big of a change would there be. Im going with the 8 3/4 because I plan on doing more with the engine and trans/tc. Im not worried of my highway gears because it'll only be driven in town.