Depends on what you mean by rip it apart and build it up. Are you talking about replacing any of the lower end rotating assembly? If you are then don't worry about it and just get an LQ4 because the blocks are the same.
Both the LQ4 & LQ9 have a good solid foundation to build off unless your looking at going over 500+ HP.

 

id like to have around 500 on spray, and by rip apart i mean fully complete rebuild and yes bottom end work if needed

 

then no, just save a few bucks and grab an LQ4 block.

 

if youre building a motor and just need ablock just buy a new bare block

 

if you already have all the parts you need then yeah.
but if you need the oil pan, valve covers, timing case covers,
windge tray, pick up tube, and so on, your better off getting
a whole motor.

 

true but he has a truck already...the present motor as everything to carry over...but yes either way works out..

 

ill prob just pick a whole motor, cuz im gonna keep the 5.3 together much as i can because i have a friend with a 99 5.3 with 80k miles im prob gonna give my motor to, or i might cam it and give it to my dad for his 72 chevy

 

i have a 03 lq9 what would be good to do to it?

 

Change to an electric fan and have it tuned.

 

THREAD JACKER!!! lol j/k yea swap the fans for sure