?'s about my new truck

Hey guys, I'm trying to figure out some things about my truck that I can't quite put my finger on and who better to ask. My first thing, when I'm riding in my truck with the a/c on I notice that there is like a rattling noise coming from the passenger side of the dash. It happens sometimes when I'm riding without the a/c on but only when I hit big bumps. I'm beginning to think that the blower motor might be loose or the machine or whatever that adjusts the settings on where to blow the air might be going out? Any suggestions?

The second thing, I'm thinking about replacing the wheels on my truck and I'm trying to figure out the back space on it. I think it's either 3.75 or 4.5? Does anyone know for sure? Thanks for any help guys I really appreciate it!

 

Nobody?

 

I've had my blower motor replaced for that reason and my wheels are 4.5.

 

I figured that's what it was. I'm about to buy some wheels that are 4's. Not sure if they'll fit though. Anyone else?