Times 3.. I don't think the problem is in the box. When you assembled the kingpins originally you mentioned the front being hard to turn but was getting better. It's probably still to tight and should be disassembled and measured. When properly "fitted", the new kingpin should slide into place with a minimum of pressure but no appreciable play.

You''ll need a micrometer and an adjustable reamer at a minimum and after measuring the kingpin, set the reamer for another 1 to 2 thousandths over to give the pin room. Pass the reamer through with a few spins round and test fit the kingpin back into the bore. Rinse and repeat if needed. ( Caution, once you remove material, you cannot reinstall it! go to much and you'll be forced to replace the bushing!)

There shouldn't be any "break-in" period, and everything should move free and easy when assembled. HTH