Looks like your truck engine is original. Congrats, you found positive documentation. One theory would be once they decided to get rid of left over 235's and 261's, they decided only one frame package would be built for them and that frame package would only have those engines and that package was a K.(plus a 283 V8). That would make it more manageable and "sort of" match the public sales brochures which don't mention those engines. It could be explained to the utilities companies, surveyors, ranchers and farmers that bought 4x4, the "public" could not afford one for hunting and playing around as today.. Most of the 4x4 stuff I have had pre 66 has been owned by State, city or utility and then auctioned off and finally sold to 4X4 enthusiast....Yours is pretty darn Valuable/Rare in the market place.....BUT as an example how whaky the info can be, The TSB Director who wrote this (your link) uses an example of serial number suffixes at the end of the Truck Suffix list. His example uses an L, there is no L in the list. If the L is "left over" from a list in 1962, why use it when explaining the "new" suffixes? This post has been very informative with great documentation, albeit sometimes hard to rectify fully. I think we got to the bottom of this and saved TC's reputation.
