Cleveland's RULE

Well, the easiest way to tell if it's a cleveland is (second to the valve cover thing as stated) is to LOOK at the corner of the head there will be a little 2 or 4 cast into the head, pretty easy to see.

There are two spots to check for #'s on the block. First is just above the oil pan rail near the starter on the side of the block. There should be something like DOAE-CA or something similar, what you are interested in is the code below that. It will indicate the year and month the block was cast. letter indicates month A= jan; B= feb; C=mar etc...

Better esplaination:
http://www.mustangmonthly.com/howto/5801/index4.html

Then there's the VIN, you can check the VIN on the car: (on the '70 I think it's still under the hood) look at inner fender on the driver's side, probably ~12" back from rad support, it may be hidden by the fender being bolted on. You could also check the title (should have the VIN on there, or the door tag if it has one.

The motor code will be the 5th digit in the VIN:
http://iml.jou.ufl.edu/projects/students/Blommel/70.htm

As for the matching ##'s on the block, at the back of the motor, near the bellhousing, on top, there is a stamping that should be visible, should indicate the last 5 or so digits of your car's VIN if not then it's out of another car. I'm not exactly possitive as to where the stamped VIN is on the block because I havn't even looked a clean bare block in soooo long. The area may be covered in paint and/or be difficult to see, = very hard to check with the motor in the car, with the hood on (In my experience).

Hope that helps,