Thumbs up on the color choice here too.
The original mirrors were mounted to the cowl.
http://www.picturetrail.com/sfx/album/view/23314896 You may even be able to find the holes looking up from below (inside the cab). If you want to go this route more info is available. Just ask.
My 2 cents though is even though I love the look of the original mirrors, they are pretty tough to actually use. For a driver I prefer aftermarket mirrors. How hard did you look for mirrors that would fit the holes you already have?
