1969 gmc with a 157 in wheel base?

[gcm]

So for some time I have been looking all over for a cool 67 to 72 dually to resto mod ya like the ones in fast and ferrous but I actually wanted mine for towing my horse trailer. Now from everything I have seen and read the 157 inch wheel base didn't start until 70. Or more accurately the production numbers aren't known for 1969 and then we have them for 1970 and other. Words. I was told by another collector that if the production number isn't listed but have aren't model number and other info that means usually less then 1000 where made. Now I attached a photo that the seller sent me from what I can decode this is a original dually from 1969 right? The owner says he got it as as 68 but the hood wasn't correct.