The frames from 60-62 are completely different as are the suspensions on them. They are an "x" style drop frame as opposed the the newer "ladder" style frame they started using in 63. They used that style until 87 or so I've read. The front crossmember on the "x" frame is part of the torsion bar system and is also very different from what's on a truck with coil springs. You should have a lot of years to choose from. Obviously, the best fit will be 63-66.
