I believe the 848 head came out sometime in '56, and it became the standard, and probably the one and only, 235 head, or it at least became the standard replacement head for all 235's back to '53. That assumption is based on the '58 and '68 parts manual listings, which only show that head for the '53-up 235's.

Curt
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1953 Chevy 6400, 1957 Chevy 2dr Sedan
--"Mediocrity is easy, the good things take time"