Universal flexible hoses?

See page 44 of this slant six drag car build thread,
has photos with part numbers and descriptions of upper and lower radiator hoses that connect a slant six to a v8 style aftermarket radiator

Covalt - "Project 65 Valiant" - Page 44 - Slant Six Forum

if the lower hose mentioned in the build thread does not work for you try a
Dayco 81261 flex hose, it has the correct end diameters to connect a v8 radiator to a slant six water pump.