I agree, the work truck sheetmetal is usually bigger than the pickup stuff. A couple quick measurements should answer this. I realise you don't have a grille to measure, but you could measure the space, or measure a fender and see if it's the same.

There is no formal VIN numbering or location back then. The feds required the VIN on the left dash area ~1970, and the numbering was standardized when they went with the 13 digit VIN, although it's still not exactly the same across manufacturers.

The internet is a good source for info, and there are spotter's guides. Research and print out the stuff that you need.

Good Luck