Irwin,
I too have the royal king pin set. The needle bearings are actually very short bearings (0.500") and the design stacks two of them to get the same length as a standard bushing. Plus they include thrust bearings - which are similar to those in a standard king pin rebuild kit.
The steering knuckle is not opened up at all as far as bore is concerned and the needle bearings come with an external bearing cage with an OD that is a light press fit into the stock bore on the steering knuckle.
The king pins themselves are turned down on the ends to accomodate the needle bearings. I dont have a micrometer handy, but they look to be turned down to .75 inches.
The pins are made of stainless steel.
If your knuckles are not egged out - this would be an easy kit to make yourself. Torrington bearings were used in the 1/2 ton kit (part# B-138 stamped on the race). The clearance between the pin and the bearing diameters seemed loose to me, but when the race is pressed into the knuckle, it feels pretty good. The pins are also drilled on the ends and threaded for grease zerks on the ends and side drilled to allow grease to get to the bearings on the diameter. The stock grease zerk locations will not work as these ports are blocked by the outer bearing race of the needle bearing.
I wouldn't hesitate to do this now that I have seen what all is involved with the kit I bought for my suburban.
Good Luck!
