I am hesitant to reply because every time I do I get critiques from the 30+ post wonders that inhabit the site lately, but here goes. Here is a picture of the mast hole you describe. There is a similar shaped plate that covers it on the inside. I have seen this on a couple 47's and one 48 I have owned. You can also see the smooth cowl pretty well.
https://www.flickr.com/photos/advance-design_parts_co/8593171495/in/set-72157631870734114The column bracket appeared to be the same as the later models, I haven't sold it so I will look around to double check, same on the gauges as I know I still have them. Part number on the column brackets is 3686722*16 and 17.
https://www.flickr.com/photos/advance-design_parts_co/8625359671/in/set-72157631870734114I have also seen 48's with and without the rain channel which was probably a running change by assembly plant.
