worn front end

I can't figure out if my pitman arm is worm or is it the center link?Seems like the steering box is fine but when you turn the wheel where your pitman connects to the center link there is about 3/8 to 1/2 play there.What do you think I should replace??

I had this happen once with a car I built using a Vega box and an aftermarket Pitman arm. I did what Denny is suggesting, and found that the splined hole in the aftermarket Pitman arm was machined a few thou oversize. The spline on the Vega box has a slight taper on it, so the problem was easily corrected by adding a flat washer between the pitman arm and the lockwasher under the nut which holds the Pitman arm in place. This forced the Pitman arm down a bit farther onto the tapered shaft, and the slop disappeared.