Hello and welcome to the forum poolecr.

I just performed a complete overhaul of the 3.5L in my old 1997 over the past summer. I do not recall any kind of loose fitting crank sprocket at all. As far as I remember it was a really snug fit going over the woodruff key. So was the harmonic balancer.

I noticed you mentioned that the sprocket was something you would want to replace. I think you are on the right track. You are right about the crank bearings, the wouldn't wear enough to cause a visible wobble problem with the crank pulley. I mean, I suppose they could get worn pretty badly, but you would probably experience some severe engine performance problems before you would notice an engine wobble.