Quick 5.3 info
LC9 / LH6 / LH8 - Gen IV - Truck - Aluminum - 2005-2009+ - 326 hp / 350 ft-lbs
Little brother of L76
LMF / LMG / LY5 - Gen IV - Truck - Iron - 2007-2009+ - 326 hp / 350 ft-lbs
Little brother of LY6
LM7 / L59 - Gen III - Truck - Aluminum - 2003-2007 - 310 hp / 335 ft-lbs
First all aluminum 5.3
LM7 / L59 - Gen III - Truck - Iron - 1999-2007 - 295 hp / 335 ft-lbs
Little brother of LQ4
Quick 5.7 info
LS6 - Gen III - Car - Aluminum - 2001-2005 - 405 hp / 400 lb-ft
H.O. version of LS1
LS1 - Gen III - Car - Aluminum - 1997-2004 - 350 hp / 375 lb-ft
First Gen III V8
Just depends on what year either motor is that being said you can always bore the 5.3 out to a 5.7 but you cannot bore a 5.7 to take advantage of the 6.0 4.00in bore one smaller reason not to go with the LS1 is if something happens to the block they are much more expensive to replace than the 5.3 block in the end both can make great power hope this little amount of info helps and here's a big ol link to some more
The two links provide a massive amount of info from power output to weight and dimensions, problems from the factory and what motor replaced etc etc etc
http://www.pirate4x4.com/tech/billav...SPrimer/Part1/
http://www.pirate4x4.com/tech/billav...SPrimer/Part2/