if you wanna get technical about it saying "sixties camaro" references two things:
1. a 1960 camaro
2. all camaros from 60-69

as there were only 67-69 its generall said as late sixties or 67-69 camaro

ive been around muscle cars all my life, my dads had 3-4 camaros, ive been going to classic car shows since i was 9, my family even put one on for 5 years....never heard someone say 60's camaro to describe them.... thats just me though