I am mid way in converting my '59 small window cab into a big window. This is not for the faint of heart. I am taking many pictures that I will try to put into an orderly series after I have finished.
I bought an entire big window '58 long bed step side (less front fenders and grill) for $300. It was better than the one I started with. For $20 the guy pulled the cab and brought it to my house, what a deal! Anyway, I sectioned it up and saved the roof (which I needed) and the entire rear panel cut below the latches to the drip rail.
I have completely disassembled the window frame from the outer panel and am prepping the pieces for installation. The inner panel on the big window is four sections, the small window is all one piece. I cut my existing inner panel in half getting it out. The big frame was rusted out above the window on the inside so I had to fabricate that piece. As it turns out, the top of the small frame is the same profile and the bottom of the small frame is the same, less one bend. A little time with the metal brake at work and my MIG welder and I'm back in business.
The big window has many reinforcements, starting down at the door latches and crossing the rear of the cab. I am working to put all of these back just like they were originally. The posts also receive reinforcements that tie to the door frames.
That is as far as I've gotten. I will add more as I progress and write up a list of reasons why no one should do this at the end.
I have a MIG welder, a spot welder and reckless confidence, hopefully that is enough to see me through. :p