Look on the back of the block, passenger side, just under the head. I usually look at it from under the car with a flashlight if the engine is in the car. That is the block casting #.

On the top of the block, to the driver's side of the distributor, is a cast date code. It should be three or four digits.

There should also be stampings on the front of the block, just under the passenger head which will have a (usually) two letter code like YT and a numerical code. The letter code is important.

Heads have a big pair of numbers cast in the center exhaust runners, one digit on each runner. Numbers should certainly match left and right. Some heads have different variations by date as well, even with the same casting number.