There are two types associated with your 216 originally, open element and oil bath (2-sizes).
https://www.flickr.com/photos/advance-design_parts_co/8250844197/in/album-72157632186114015/
Oil bath type, referred to as a 1-pound (Option 216D, $3.65 installed).
https://www.flickr.com/photos/advance-design_parts_co/17057189590/in/album-72157651718017649/
https://www.flickr.com/photos/advance-design_parts_co/8129088452/in/album-72157631867396207/
Oil bath type, referred to as a 2-pound (Option 216E, $4.70 installed).
https://www.flickr.com/photos/advance-design_parts_co/17057189770/in/album-72157651718017649/
https://www.flickr.com/photos/advance-design_parts_co/18996552503/in/album-72157631870734114/
Both the 1-pound and 2-pound are listed for the 3100 Series truck in 1947 price guides and 1947-48 Salesman Truck Data Book.