Building a 5.3
 

I'm building a 5.3 to put in my 2000 z28 and trying to get 500-600 hp any suggestions which would be the best way to go

Re: Building a 5.3
 

Again.... wrong forum. As you already know the 5.3 is an LSx format engine, so I'll move this from "LT1 Based Engine Tech" to "LS1 Based Engine Tech".

There was more than one 5.3L V8 used in the trucks in 2003. Does it have an iron block (LM7, L59), or an aluminum block (LM4, L33)?

Did you read the article on building the 5.3 I linked in your post on the "New Member Intro" forum?

5.3L LS Small Block Build - Here Comes Modern Mouse! - Super Chevy Magazine

Are you looking for 500-600HP at the flywheel or at the rear wheels? 500HP is easy at the flywheel.... 600HP at the rear wheels is a project.

Re: Building a 5.3
 

Easiest way to get there with a 5.3 (500 or 600 hp) is going to be with a stock bottom end. Install some cheap head studs, open the ring gaps a bit and put a turbo on it. They'll do 600 whp for years and if you do manage to screw it up you can get another one for cheap.