I have the same pump on my 67. (3975928) From what I could gather its a L88 or heavy duty pump sold over the counter that they offered up through the 90's. If you look on yours you should see the date cast into it. Here is mine for reference of the date. If yours does not have a date then it is probably one of the early ones from the 70's. Maybe someone else will have better info but that is all I know of them.