It really isnt as complicated as most make it seem. I took it as crank hp not at the tires because 600whp at the tires n/a is an extremely stout setup that takes alot of attention to detail. It can be done but requires more cubes and alot of airflow.

500wtq is alot but doable with strokers. Again I took that to mean 500+ on motor which would be mid 400's at tires.

So many posts go by and nobody clarified this issue til later in the thread, was it crank hp or rear wheel hp that he wanted? HUGE difference, but doable either way. Some heads cam LS7's are 600whp. Thats about as stout as it gets without spending BIG bucks for some really worked over heads and custom intake. Your typical intakes will not cut it.

I was also talking only engine build not the entire car and support mods like trans/gear/axle, suspension, etc. That can easily add up.

As others suggested, if you need to make big power and rebuilding from scratch, do a big bore big inch motor. Always the best way to start a n/a build. But its very likely he could hit that number on stock crank, but with good rods and light pistons with strong rod bolts. It should handle 7500 max rpm with a peak near 6800-7000. If the heads/intake are worth a darn, it should make 500-530whp depending.

Its not gonna be a great driving street setup but thats not what he asked. He wants a pump gas powerful car.
On a budget, stock crank, new piston/rod setup rev it up with the best heads you can afford. Actually would be best to use a 6.0 block for that 4" bore to take advantage of larger valve/less valve shrouding. Well put together package will make those numbers

 

For those who have been asking, I meant 600+ crank horsepower. As for the strokers and borers, the build setup that I've been looking at calls for a 4" overall stroke, the problem is my block can't be bored out any further, sonic tested it and it showed that they were already as thin as they could safely be? Not 100% sure if thats how GM made them or if a previous owner did something to them, cause the cylinders are sleeved (Tho I can't believe that GM factory sleeved their blocks). Current dimensions are the stock 346.

 

If your talking about an stock ls1 block, they cant be bored more than a .005 cleanup (I think thats right). most rebuilds go 3.905. stock is 3.898. stock stroke is 3.622.

and yes, they are sleeved from the factory. its an aluminum block. to get a 4" bore, you need an LS2, or 6.0l iron block. they can go 4.015 or maybe 4.030 (ls2). not sure on the 5.3 blocks.

or get an ls3 = even more work.

why dont you tell us how many cubes you want, and someone will post the most economical way to get there.