All bs aside a stock 5.3 makes about 220hp to the wheels, if you manage to get 310-330hp from a cam swap call it a good day.
The Fleet...
2003 Suburban- 5.4 L59 331CI 10:5.1 Compression -Built by ME
2004 Avalanche- 5.7 LS1 -NOT built by me
2005 Silverado RCSB- 5.7 LS6 -Built by ME