Found this in the TDR web site:
http://www.turbodieselregister.com/f...threadid=81370

my '03 H.O. had the tick at idle since new. it sounded fine at higher rpm's but always came back at idle. I found a cure and it's not pretty. Turns out that the H.O. has a notch in the bottom of the piston on one side to allow clearance for the oil cooling nozzle jet. if a piston is installed with the notch on the wrong side, the piston will lightly tap the oil nozzle on the down stroke and make the tapping noise. This was the case with mine on #5 cylinder. chryslers fix was to replace the short block @ 10,000 mi.. there was no damage to the original block that I could see. after 18 days in the shop the truck is back together and I have put 1,100 miles on the new engine and it runs the way it was designed to.

My 04 has the same tick after starting but seems to go away after warming up. It has been to cold for me to really check tho.