4L80E behind your LS. Two things to look out for, the first one concerns the transmission mount, mine was done using a stock type mount which involved cutting into the semi circular body reinforcement which I was not happy about. A suitable custom mount would avoid this but involve some work, worth it in my opinion. The second thing concerns the oil cooler fitting out of the trans, it was left to rub against the tunnel, a very slight bit of relieving will fix that. Mine is a right hand driver if that makes a difference.