IC engines with transmissions take up vastly more space and weigh quite a bit more than electric ones do which limits the impact of energy density.

Electric has ~4,200 lb to work with before weigh for components before you consider the weight of fuel. https://www.energy.gov/eere/vehicles/fact-620-april-26-2010-...

Mack trucks get ~6.5 mpg, so a 350 mile range would take ~5 Tesla battery's ~6,000 lbs. That's a little low, but far from useless just add how battery swaps and it's completely viable.

Long term, the move to in road charging means electric trucks will actually save significant weight over IC engines while also having unlimited ranges. http://money.cnn.com/2015/08/18/technology/uk-electric-cars-...