My 2004 Chevy pickup is built so light that I believe that the 1968 Impala I drove in high school was a tougher vehicle. With the right rear springs and gears the Impala would pull as good as my new pickup.
But, the mileage would be a little worse. The Impala got 20 MPG empty going down the road on yesterdays gas. The 2004 Chevy pickup gets 15 going down the road on today's gas but, it has a overdrive. Take into consideration today's gas and the Impala would not do as good as the pickup running empty on today gas. Give it a overdrive, some modern cylinder heads, and then, it just might!
The Impala could have used better stopping power too.