Chimi already covered it, but HU against Top set you should fold. 12 out's twice isn't enough overlay when you don't have a ton of dead money in the pot. Remember that even if you make your straight your opponent will have at least his boat re-draws so you can hit your straight and still lose.
http://twodimes.net/h/?z=1363331
pokenum -o qh as ac jd - kd kc qd 6c -- ks 5c td
Omaha Hi: 820 enumerated boards containing Ks 5c Td
cards win %win lose %lose tie %tie EV
As Ac Jd Qh 273 33.29 541 65.98 6 0.73 0.337
Kc 6c Kd Qd 541 65.98 273 33.29 6 0.73 0.663