63-66 Chevy frame v.s. 67-72 Chevy frame identification

[88k5jimmy]

I've done quite a bit of research regarding the subject, searcing online and on here but would still like some input:

What are the visual differences between the 63-66 and 67-72 chevy short bed half ton frames? I know you can run the vin on the left drivers side top frame rail on the 63-66 and it "should" give you the right year, however I have looked at a 66 frame that had the 6 digit for the year (verified with the vin on the cab it was a 66) and an advertised 63 or 64 frame that did not have a digit signifying the year but had all the signs of a 63-66 frame (not torsion bar front, trailing arm rear, correct front bumper, etc). So I'm under the assumption there are some inconsistencies when it comes to whether the year digit is stamped on the frame. One of the visual differences I have found between the 63-66 and 67-72 frames are the front frame horns where the front bumper meets. 63-66 has two holes in the front frame rail to mount the bumper, 67-72 has one hole in the front frame rail and an elbow bracket with hole on top of the frame rail for the top bumper mounting hole. Are there any other obvious signs I can look for? I know the frames are very similar from 63-72.

Thanks