They are both convex and can be flattened a little to make them fit tighter. I also stake mine in four places as per the manual. Your only doing the job once right? No sense in being lazy about it and if you check the grease on a reasonable basis, you shouldn't have many issues and need to swap kingpins again in your lifetime.
I doubt you'll see anything more than a tiny bit of grease if any, come out of the top. Most of it will ease out between the thrust bearings between spindle and axle if I remember correctly.
Jeff
