do you have any pictures you could show us? i do not know of any wrap around rear glass in those years. if its a 60s model the similarities would be from 60-63 with wrap around front glass. 64-66 no wrap around front glass. 60-61 had distinctly different hoods while 62-66 all had basically the same hood. also the grille and headlights can help identify. 60 and 61 has 2 headlights on each side. 62 has single headlamps on each side with an oval shaped bezel. 63 had round headlight bezels while 64-66 had square. 61 is quite noticeable with the in hood turn signals housing bearing the bowtie design. below is a list of examples of each year.

Hoods and front grille examples
1960: http://web.engr.oregonstate.edu/~merriss/Pictures/Truck%20At%20Sunset.jpg

1961: www.stovebolt.com/gallery/shott_mike_1961.htm

1962: http://www.zianet.com/SLlover/we62ChevyPU.JPG

1963: http://www.classiccars.com/classifieds/images/73/7321-23197lg.jpg

1964-66: http://pigeonmaster1.tripod.com/u21.jpg

windshield examples
1960-63: http://www.americandreamcars.com/1963chevytruck012704.jpg

1964-1965: http://pigeonmaster1.tripod.com/u22.jpg

many more examples can be had by our gallery here: http://www.stovebolt.com/gallery60-66.htm
hope this all helps.