There is a secondary VIN stamped on the frame. It is just behind the steering box on TF trucks. I'm not exactly sure where it is on the 60's trucks. If they both match you are OK, if not.......
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine