I believe the GMB 130-1043 water pump is the 5/8 inch version for the early engines. That 5/8 inch pump is usually cheaper than the 3/8 inch one.

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