1995 Land Rover Discovery 3.9 V8

I just finished rebuilding the heads and replacing all of the gaskets. However, I did not redo the bottom end. Everything sounds fine besides an exhaust leak from the passenger side. However, on the back side of the block on the drivers side, it's leaking water. I'm guessing it's from a head gasket. It's brand new, but I suppose the block could be warped or cracked. Do you guys think I could use gasket sealer or jb weld to stop this water leak?