[LS short box]

So a I hate to be Debby downer but a 2004 6.0 is 20 plus years old. Have you done the basics like a compression test? What trans and if auto what stall?
Head wise L92's are hard to beat cost wise. No matter what you will need aftermarket valve springs and push rods for the cams you listed.
I would talk to BTR about vacuum for power brakes per the cams listed above.
So 500-550 hp at the crank or at the rear wheels? If you want that at wheels a stroker may be in your future.