I bought a kingpin set to install in my original 37 spindles, took the whole thing to a good machine shop and let them do the fitting. This shop is known to be expensive but I think their the best, and you get what you pay for. Cost was about $80.00. When I put them on, they fit perfect. Even though I have the equipment to do the job, I didn't want to take any chances. Dennyw is right about the fit, snug and you should never, ever force the kingpin. Good luck.