lower unit for evinrude/johnson motor

[barely-a-wake]

I am wondering if anyone can tell me what year my lower unit is approximately. I believe it is late 60's early 70's but not sure. I am needing to know because someone is needing it and is wondering what years interchange. He has a Johnson 25hp 1974 motor and says his looks just like mine but wants to be sure. I'm certain mine is a 35hp Johnson. Any help would be appreciated and you can see this lower unit on ebay under the #2417572008. Thanks again. Kevin from Virginia.