I was wondering when installing driver door sport mirror on my 72 cs should it go in the holes that are already there from the factory mirror with no problems? Or do I need to drill a hole to make it fit? One side go in perfect but the other side it appears I might need to drill a little to make it work. I haven't played with it much, but I will be soon.

 

It should fit without modifying the factory holes

 

What about if the mirror came off a 73-78 cutlass?

 

70-82 camaro firebird used the same mirror as 71-72 cutlass 442. 73+ cutlass mirrors are different. They hold the mirror to high and at weird angle on the door.

 

Eventually I would like to do the same on my 72' 4 door. Would the mirrors still be the same?

 

Yes, so long as you don't use the 73+ mirrors you should be fine. Maybe give John McNeel (2blu442) a PM and check out his stash. He's closer to you, in Oregon. His pricing is very fair; only thing you need to anticipate is cross border shipping. Nothing in the Picknpull locations near you for either - I just checked.