You can stroke up to 4" without many issues but I think it would be a waste. The 5.3 is a strong enough engine without having to stroke it. The cylinder walls are too short to reliably handle the 4" stroke and the pistons coming down an additional 3/8". Stick with the stock stroke, bore it out to LS1 size, throw some forged rods, forged pistons and quality rings in there and go have fun. Save the $800 crank money for a shot of nitrous or something else. Do you want to spray it or do some forced induction? Be sure you buy the appropriate pistons for your plans and plan your compression ratio accordingly.