I had a 62 4 door Impala for many years. 4000#'s is right! Boy what a smooth ride though ;-) Mine had the 235 with a manual 3-speed. I never did mod a thing on it (stock)... but it was the same sluggish response below 60. But hit a hill at 70 and the motor was in the torque curve I guess... up the hill no problem! 13 mpg!
FYI... I hade the same with the 3 speed. Hope that helps you decide.
Clyde
