I've not dealt with the LS series motors, just your older SBC's. Ive seen motors with spun bearings rebuilt before, it depended on the damage caused. I would take the motor out see what damage is done, at the worst you need another block.
Did some quick reading and found that these motors are able to be rebuilt, it really depends on how long you ran it after you lost oil pressure and whether you sent part flying in the crankcase. If you turned it off when you lost oil pressure you should be able to get away with a crank, bearings, rings, having it magnafluxed, and line bore at a good machine shop. It all really depends on the condition of the block and the caps as they tend to crack in the saddle when overheated.
Here's a site I found some information on: http://www.chevyhiperformance.com/techarticles/0708ch_block_repair_basics/index.html