I HAVE A 2000 GMC SIERRA WHIT BIG MILES ON THE MOTOR AND I LIKE TO REBUILD MY MOTOR WHIT MORE HP ANY AIDEAS FOR THE PARTS I CAN USE  

Well, a 5.3 is a good motor to start with, because there are a lot of performance parts available for it. SLP has a lot of parts for it, like high-performance cams, rockers, headers, etc.

It's really going to depend on how much money you want to put into it. I would personally find some high-flow, high-performance aluminum heads, a mildly aggressive cam, maybe a supercharger, if you want to go that route. Edelbrock, Comp Cams, Holley and all those guys have a lot of stuff for the Gen III and IV small blocks. Hope this helps. Let us know if you have any other questions.    

I would look for a junk yard or ebay 6.0L. This would be the bigest bang for your buck