Well what kinda things u wanting to do to it?
If ur wanting to do a cam then i have a parts list with links as I'm ordering things for that now.
But a good place to start is ls1/2/6 intake manifold swap.
There's also a turbo kit but its expensive...like way expensive
For any transmission needs I highly recommend tripleedgeperformamce.com
Also some really good write ups over on ls1tech.com in the ls4 performance section