If the kingpin is Titanium (which being an older one, is likely), using a Titanium-coated drill jobber and lots of oil and patience, you should be able to get a hole that an E-Z out can latch onto. Start with small diameter bits, not too much down-pressure, get a 'pilot' divot, go gradually larger in bit size until you match the E-Z out's diameter. A 1/4" or 6mm E-Z out should be big enough to get some traction, especially if you 'bake' the baseplate as Claude suggested. A few dabs of high-quality penetrating oil (once it's cooled from baking) before you drill wouldn't be a bad idea, either. If no penetrant oil, use a soak in gasoline to break down the LocTite. E-Z out will screw into the hole you'll drill, and let you torque counter-clockwise to un-thread the nub of the kingpin. The take some down-pressure to work, so clamp the baseplate down when you try getting the E-Z out to work. Go Slow, and don't hammer the E-Z out unless it slips. Tap it with a dead-blow to re-engage it if it does slip. If none of this works, ship it back, let Sparky have at it.
As for bushings, it's the spherical pivot in the hanger that's the issue. Notice how Radikal bushings have a flat side, and a curved side? The curvature is needed to fit around the spherical pivot and maintain constant contact between the bushing and hanger. Put a Rad bushing in flat-side towards the hanger, and the hanger will 'flop' loosely until it bumps into the bushing. That extra 'slop', with your weight on it, is gobs of sudden Torque against the kingpin once the hanger meets the bushing. This sudden jolt, repeated a few thousand times, equals metal fatigue, which leads to failed kingpins. Use the bushings correctly (and not over-tensioned), and there's almost no chance of kingpin failure. Realistically, there's no design flaw with the truck, but there's ample opportunity to have the end user misuse the bushings and create the metal-fatigue issue.
If you decide to use other bushings on Radikals (something I'm sure they wouldn't recommend), hollow out a divot about 12mm in diameter that's at least 5mm deep right outside the existing hole in the bushing. This divot, or contoured cavity, fits around the spherical pivot, and keeps the flat surface of a bushing in full contact with the hanger. Again, don't tighten down the kingpin locknut much, as you don't want compressed/deformed bushings on this truck. The idea is instead to not have 'slop', and to let the bushing reactively compress under turning loads only, not to have the bushing 'pre-loaded' by overtightening the locknut. Hence, picking the right durometer of bushing becomes pretty important. I've done a 'reshaping' on probably 50 bushings, where I trim the outer diameter to effectively change the turning resistance a bit, which gives a Radikal user a few more options in 'steering feel'.