http://www.jegs.com/p/Chevrolet-Performance/GM-Goodwrench-Truck-53L-LM7-L59-285HP-Crate-Engine/1696860/10002/-1
3yr 100K warranty - and no core charge with Jegs, so you are free to sell your old engine to someone (and someone will definitely buy it to rebuild or hot rod)
LS engines aren't cheap!
p.s. I have a Goodwrench 4.3 V6 in my Blazer. Seems to be a real quality piece. Was only $2000. About 15K on it so far. Never have to add any oil between oil changes, and that is excellent for a rebuilt engine.