1970 Medium Duty Investigation

[lgvl]

So i'm currently sitting in quarantine waiting to go to work offshore and of course i started perusing FB marketplace and came across this. Here's the seller's information:

"1970 GMC C 55 ??
Vintage 1970 flatbed truck with a V8 with a 5 and 2. Also an auxiliary transmission that you can shift in low and top speed is around 18 mph. There is a very heavy winch with approximately 150 feet of cable. This truck was used to pull heavy loads at a slow speed."

I'm interested in decoding the VIN if anyone can point me in the right direction. I've been searching high and low and haven't come up with much.