Dan,
On your Probe, I would think you would want to choose between a 225/50/16 or a 245/45/16. Both have the same diameter so gearing isn't effected. I would try the 245 as you have a front-heavy FWDer. I would test fit them but if I remember correctly, I ran that size on my GS GT when I was Soloing one in 1994-1995.