I agree, I would go with a later casting if you want to have an oem head. I wouldn't go with anything older than a number 4.

The casting number is located on the rear of the head, pressed up close to the firewall. Its impossible to see it with the head on the block in the engine bay. The best you can do is feel it with your fingers, and look for a grease imprint. Reach in from the driver's side.

That being said, I replaced a number 4 which had several cracks and bad valves (see photos below). I went with an AMC head, and have no regrets.

1989 Trooper, 2.6
1989 Trooper, 2.8
1992 Ford F-350, 7.3

My Photos