help needed with silverado question!!!

i am looking into buying a 2002 z71 silverado and i need to know about the 4 wheel drive... i was wondering about the posi track i want a good 4x4 drive for the mountains and if the clearance is good with a stock z71... and if there is other options that i should get with the truck that would help out i noticed the plow package had a tranny cooler and a better alternator is that some thing i should look into geting?