C10 4x4.... why's it not a K10?

[69stepside4x4]

Well I just got home yesterday from picking up my new truck, a '69 C10 4x4 that I have know of and coveted for the past 20+ years. The owner during that time finally sold it to ME and I drove it home (525 miles) without a hitch!

My first question is: I thought all 4x4s were K-series (the Vin even starts out: KS), so why is the fender badge a C10?

Secondly, it apparently (learned this over the weekend when I picked the former owner's brain) was a 6 cyl (250 or 292, he couldn't remember) from the factory. He swapped in a moderatly built 350 but kept the stock 3sp and axles as they were. On the highway top end was about 55-60mph ()w/ 31 inch tires), I originally thought 3:73 gearing, but he seemed to think 4:11...... what are any of your thoughts (of course I will crawl around and figure it out eventually, but I am sitting at my desk at work and want to know!)

Finally (for now), is there a VIN code decoder I can find (the SPID decal is missing from my glovebox and I couldn't find a build sheet under the seat) that would help me know more about the vehicle? I called GM today for a restoration kit, but they were always on voicemail (must have cut that position during the Government takeover).

Thanks!
Mac