The only difinitive way to tell is to pull the oil pan and visually confirm. The engine code stamped on the land in front of the right side cylinder bank supposedly can be used to tell but there are many blocks that have the same codes or even casting numbers that can go both ways.
Go find out what the numbers/letters are stamped on that land and also get the casting number which is on the back left side of the block. Let us know what those are and we may be able to pin it down....maybe.
