Frame vin locations

[iwlbcnu]

I have what I think is a 74 chassis, the main frame vin location is missing the month letter. I am familiar with the other locations, and have cleaned under the passenger floor, and the rear shock mount area, but can't find another number. Weren't all frames double stamped? I can't find the impression that is usually present.

 

[FordBronc]

As I learned from others on here.

 

[iwlbcnu]

Those are the three I am familiar with, and can only find the front one which is incorrect.