You definitely want to keep the LS crank too, there's no reason to put a B16 crank in a B18 block unless you're trying to build a B16B type screamer.

There is one OEM crank that offers more stroke than an LS, it's the B21A crank from 3rd gen Preludes, but I probably wouldn't do that without a sleeved block (high lateral cylinder forces at higher RPM).