If you have a 24 valve engine, look at the top right side of the timing gear housing (front of the engine, below the upper radiator hose, on the right side, in-line hight wise with the VP44). There is a little black plate with the engine serial number stamped onto it. It will also have other important engine information on it, such as compression, and horse power rating. It should have a number on it similar to 56789879. The first two numbers (either 53, 55, 56) will be the block serial number.
-Rich