Loaded question. depends on HOW MUCH power you want to make, and what you plan on doing with that power? Off road? on road? mild power or crazy tire exploding power?
electric fan is good for some easy gains in power. have not seen under drive pulleys for our 5.9 motors for a while, but they might still be out there somewhere... that's 1 or 2 hp...
Another cheap and pretty decent mod is to use the later 2001 air hat and air cleaner box with a fram paper element. you will absolutely NEVER outflow that airbox unless you turbo your motor. Putting cold air intakes and K&N filters on our naturally aspirated trucks is a waste of time, money and yields ZERO gains.
outside of that, doing a re-gear can net you some real grunt out of the hole and really put a noticeable change in the **** dyno. The 3.94 gears from the SLT tow package are solid and still streetable if you dont mind losing a little mileage.
If you are looking for a noticable jump in power your going to have to dig deep into your wallet. Trust me.
Cam and exhaust are useless without doing the heads and intake. Sadly the edelbrock heads are pricey, but they are the best head right now hands down. EQ heads are okay, cannot find the RHS Indy heads anymore.
Pistons are trash cast, they will fail. get the speed pro hyper pistons best bang for the buck, get some hastings plasma moly rings.
Rods and rod bolts are solid unit and will handle all the power you can feed it.
Get the best heads you can afford, and get the Hughes/edelbrock intake with a hogged out throttle body.
Get a cam that suits your needs...(you will need to do a lot of homework to be able to read a cam card and know what it means.)
If you can fit long tube headers, there is no better, shorty headers work if that's all you can get.
exhaust doesn't need to be true dual, it can be a 2 into 1 as long as it's 3 inch all the way you'll likely never outflow it.
Then comes the hard part. do you get a later ECU and run an SCT? or do you go stand alone fuel management. The problem with standalones is our crank trigger pattern sucks and isn't widely supported... you can get a different ring and put it on the front pulley, but standalone IS the way to go for the most reliable and simplest way to adjust your own tune.
I still run the stock ecu and have never had any trouble with it, and the 2002 ECU is on the HP tuners list.
remember, Buy once. Cry once. You can have a 250hp 5.9 with some hand ported stock heads, a modified keg intake, and cam that works with the stock tune and that motor will make 250hp very reliably for a long time. Or you can spend a ton of money and do a whole motor and make 400hp for a year. Ask me how I know.
It all comes down to what kind of power do you want to make, and what are you going to use the truck for.
