waldo53,

All I know about 1953-55 235 heads is from the 1929-1954 Master Parts Catalog. It does not show an 848 head as being available in 1954.

However, the 848 head was available as the replacement head for all high-pressure 235s by 1957.

The 1953-55 Corvette's 235 head casting codes, supposedly, were:
1953: 3836066 (150 hp)
1954: 3836241 (150/155 hp)
1955: 3836241 (155 hp)
All three of these heads had a smaller diameter hole for the older temperature sensor.

Tim