VIN locations?

[Hook'em]

I have discovered that the VIN numbers on the door panel and glove box do not match the VIN numbers on the title and insurance. Furthermore, the official VIN number cannot be accurate because it has a number where a letter should be. I got the truck from my Dad and he is now passed so I can't get any more info. I believe the cab was changed out due to rust and that would jive with the VIN on the cab because it is for a stepside and the truck is a fleet. The numbers are fairly close so I believe the issue is one of reading someones writing (probably my fathers), but I am concerned about how much grief I am going to get from the DMV. I would like to see if I can locate another VIN outside of the cab to determine if it is the same or different (my luck I will find yet a third number). Any information is appreciated.