My 1954 radiator had 1-1/4 inch upper and 1-1/2 lower. I believe 1955 Second Series with 235 or 261 engines had 1-1/2 upper and 1-3/4 lower connections.


1954 Chevy 1300 engine 235 (1959)
1955 (first series) Chevy 3100 engine 261 (1957)
1927 (other brand) Model T- engine 327 (1968)