use a penetrating oil
heat the old pin, without starting a grease fire
get a drift "punch/pin" that is smaller diameter than the old king pin, and whack it hard with a 5lb hammer
Is your axle off the truck? If it is, try to press the pins out. Or, take the axle to a truck shop and have them press it out (first, ask them what their charge for 15 minutes of work is - one shop told me "minimum charge for 1 hour" = $100).
