There is plenty of room inside an EF-4 carbody-the part where the contactors, relays and all the rest of the apparatus resides. BTW, the ignitrons were replaced with solid-state rectifiers. It appears that there is little chance of arcs jumping from any of the equipment or cables to ground.I’ve seen a few.
In comparison, the EP-5 was a case of ‘five lbs of you-know-what’- stuffed into a 2 lb bag.’ Main transformer (under the floor on modern locos), smoothing reactors, accelerating resistors, Vapor Boiler, contactors, relays, etc. I would guess an arc in the wrong place could cause some of the organic materials that were state-of-the-art to ignite. Wire jackets, insulating varnish, etc.
CPM500