Rims

I have a 2002 Crown Vic (non-police). Nothing fancy. 4.6L V8. Great running ride. It just has the factory steelies on it (16x7, 5 lug, 4.5in) but I want something that looks a little more aggressive. I found a set of alloys from an 08 Ford Fusion, but I'm not sure if the fit will be right. The wheels on the fusion are 16x6.5. Will that 1/2 inch make a difference in fit?

It mostly will depend on your back spacing you should measure that to see whether is is the same on both rims. Bolt pattern you should be good. Tire size may change a little which could put your speedometer off a little. But those really should be your biggest issues.

there are a few reasons they won't work.
1. The hub bore is too small for your car(they will not bolt right on).
2. The offset is wrong for your car(they will not bolt right on)
3. More of an engineering thing, the car came with 7" wide wheels for a reason. Of course earlier panther vehicles came with 6.5" wide wheels and were possibly heavier so...