I won't say the 261's never had a 848 head but where I live I have never seen one from the factory. From what I understood the 848 head with the smaller chambers were 235 1958-1962 plus some replacements.Personally I've never seen a 848 head with steam holes from the factory which they would of surely had to of had. Please understand this is JUST MY thoughts on the subject. 1 OL REDNECK