GMC Vin decode please

[Americanrider]

Trying to find if my 70 GMC shorty was a step bed or a fleet bed from the factory. It has a steel floor fleet bed on it now and needs a lot of work. It's a 250 6cly/3 column shift. It had the vin listed on the glove box lid and not a model code like the Chevys do. Only 2 options listed: Blue paint & blue interior trim. The other oddity is that it has a coil spring rearend, which sould be listed as an option, am I right or wrong?

Here ya go: CS134 ZZ526**

Thanks ya'll
It's the Blue beater in the background.