to me Jock is a sporty looking guy who's fit, wears a jock and sportier clothes, plays sports etc. Has a more sporty look overall. Someone that just by looking at him it's obvious he plays a lot of sports. In college for example the jocks wear sports shoes, or short and sleevless shirts that you'd normally see them wear while playing basketball for example.

hunk ... makes me think of someone who's 25+, fit body, his attire isn't sporty e.g. nicely fitted jeans, shoes, shirt with a jacket