calling on the stovebolt gods

im looking at restoring as original as poss a 1945 chevrolet 1/2 ton truck, has a fresh rebuilt 235 in it now, ill be switching out the rear end gears to a 3:55 ratio 4 speed trans, what kind of milage and top speed will i be looking at?
no real idea on what tire size ill be running but will be on original rims