Keith O - I didn't see anyone chime in on your question about the spark plug gap. I had the same question/issue when I got my first 1450. Seems IH always recommended .025 and Kohler more often recommended .035. I was always told just split the difference and use .030.
Kraig - why is it that using "O" bugs you? I actually wonder when the term "Original" began being used. Was it on here? Really don't think so. By the time this site and the internet started the 61-63 Cub Cadet had been around for 30+ years. My guess is it just started wtih general discussions sometime after the 70/100 series came out. You couldn't just refer to it as a Cub Cadet since the 70/100's were also Cub Cadets - so people had to have a reference to refer to them. If I owned one and called the dealer for a part, and he asked me what model I had, what would I say? Might say the "Early" one, or the "First" one. After a few model years this becomes harder to recognize and the term "Original" becomes more appropriate. I would suspect the IH Dealer org probably would have come up with the "Original" term. As far as I know it never was used in any IH publications, literature, bulletins, parts books, etc. And as for using "O" or "CCO", well it's basically like you said for the other models, it makes typing the name easier, shorter, and just sort of gets picked up on by everyone involved.
Now, my 2cents on the seat stuff. I believe the 782 was always supposed to have the high back but originally was produced with the mid-back, and some of the early literature shows it with a mid-back (which someone referred to as a low back). Some of the later literature shows the high back as being a standard feature on the list of specifications but shows a picture of a 782 with a mid-back. I'll be glad to send anyone a copy of the literature where it references the high back deluxe seat as a standard feature and shows a separate picture of just the seat under the 782 section, but then it shows a picture of the complete 782 tractor with a mid-back seat.