Just picked up a pair of GMC 630'
 

Hey guys just picked up a couple old tandem semi's and am wondering how to identify what year they are. I can not find a listing of the big girl VIN numbers one is a DW that had a DD4-71 and the other is a HDCR that is supposed to have the 426(?) Gasser
Both are real rough and minus engine. Both have 5 window cabs ..the diesel has push button doors and wing windows, the other has wing windows and turn down handles. I am forgetting my model year details and am not certain they apply to the bigger ones anyway.