With radiators the part number on the radiator is the number in the book.
The 027 is also the number that is on the broadcast sheet.
There is either a typo or omission in the 68 parts book.
Googling the number says it is 273 but nothing that I call official.
Glen-Ray Radiators might be able to clarifying the application for this radiator. https://www.restorationradiators.com/