EMPs damage most electronics through induced currents, which are created by a change in magnetic flux affecting wiring (much like the coils in a generator passing through magnetic fields). The more wire you have, the greater potential current you generate. A Faraday Cage would reduce or prevent damage to electronics by disrupting or redirecting the lines of magnetic flux. Most military hardware that is "hardened" uses some sort of metal braided covering (grounded) over the wiring to simulate the effects of a Faraday cage, plus surge suppressors and encapsulated electronics to reduce the potential for damaging current/voltages.

Pretty sure my 70 Powerwagon will still run, as it's on points, carbed, and I have spares for everything. The only issue would be the 60 gallons of fuel necessary to go 150 miles....