If you had my truck, stock with just a K&N air filter and felt like spending $600 give or take a bit what would you buy?
5.3 Extended cab, 4L60-E, 3.42's in the rear.

 

Pacesetter LT's and you'll have enough money left over to get a wait4me tune!

 

Muffler and tuning?

 

muffler isnt gonna do much but the tune would, i would save another 200 and get some Pacesetter LT's and a nelson tune. 379.99+425.00 BUT if alllll you have is 600 get the headers and some Ls1 electric fans (100.00) and a wait4me tune (75.00)

 

You really need 4.10's and a Eaton. Trust me with you having 3.42's and Im assuming a open diff. it would make the world of a difference. I was in the same boat once.

 

LT's and a tune.

 

Easily your best options...

 

i agree with the first suggestion. save a couple more hundreds for the ultimate upgrade. pacesetters+nelson tune= bad *** truck

 

TT3000 + tune.

 

Go down to the Wal-Mart and get a big Jar for $1.89, then put the remaining $599.11 into the jar... Then over the course of time keep adding money into the jar until you have enough for a Turbo or Super Charger!!!