waldo,
You are reading it right. The Master Parts Catalog, as Bill posted, shows replacement part numbers (that's why I showed both the 54 and the 57 Catalogs' entries). The 848 head was not shown in 54 but it shows up in 57 - the 848 head first became available in 1956 and was the standard replacement head until the end of its run).
I'd be willing to bet that a Corvette-purists' discussion board would quickly (and probably rudely) state that an 848 head was not an original (year-matching) part.
Finally, other indirect evidence that an 848 head was not used on any 53-55 Corvette 235, would be the size of the hole for the temperature sender. An adapter is needed in order to use a 55 or earlier temperature sender in an 848 head.
Tim
