The heater hoses on my truck are as follows: 5/8" heater to engine, and 3/4" heater to water pump.


http://s971.photobucket.com/albums/ae197/jon63c10
1963 c-10 shortbed stepside 427 BBC T16 HD 3 speed
1963 c-10 shortbed fleetside 348 "w" 1st gen big block & powerglide