I can't offer much in the way of which engine this tach will work for, but I can say it looks to be a later unit if its factory (i.e., without a transmitter box).
I did find this post that includes a picture of an OE-1 by member 1963c-10. Not sure if they are still on here or if that was their tach that was pictured. I believe what you have is a V8 tach, but I am not certain.
https://67-72chevytrucks.com/vboard/...=392461&page=4