That's good feature, providing more replayability.
I don't think I can accept all side missions in first play...

what about exhaust can you purchase like straighit pipes?

Rear view monitor?
 

Can you get the rear view monitor upgrade for the Centuary and if so in which towns truck stop is it located?

Airport.

I think all the upgrades are random each game. They are in different places all over the map.

Correct me if im wrong.

Yes, you are correct. Every time you restart the game, the equipment is randomized at the warehouses. What you got today won't appear tomorrow.

Thanks for the replys. So I take it from the replys that the rear view can be obtained for the Centuary it's just that I need to be in right place at the right time?

Airport.

Thats correct.

Yes, they all change every time you restart the game. To me, and others, it's like they ran out-of-stock, but you'll find them somewhere else.

It would be nice if you could order any equipment. And then go back a day later to get it.

This is not good since you may not even know what upgrades are available for your truck.

I went into a shop and could buy nothing for my truck. I thought it was because the truck was in too bad condition, or there were no upgrades available for it, only now I realized that you can't get every upgrade anywhere.

So this means I have to stop at each and every repair station to find out what upgrades I'm still missing? That's just great:-x

I don't mind it so much. It makes you explore the map, and it changes every time you restart the game. For me that's just part of the uncertainty that keeps you guessing, and makes the game more interesting.