In addition to the casting numbers Mikey referred to there is also a pad on the passenger front edge of the block just at the block deck. If the block wasn't deck milled there should be some stamped numbers there. The basic casting may be appropriate for a variety of engine configurations so those stamped numbers, when decoded, will give further clarification. All that being said, these engines are so prone to modification that the original data can be rendered of minimal value. A partial tear down and inspection may end up the best solution depending on how committed to accuracy you are.

Punch the numbers you glean into Google/Bing and all sorts of info will pop up.