57-59 deluxe heater control valve

[AZ59apacheguy]

I actually went through the EXACT thing you are right now. I bought a new Deluxe heater valve for 55-59 Chevy Truck. When I got it it had a smaller diameter barb than the one going into the heater core. Do a search on ebay, or online, you can buy a rubber 90 deg 5/8 to 3/4 hose and make that work. I also went into my local O'rielly's, went to the back where ALL the hose were, looked, looked and looked and found that particular hose there. So you might luck out that way as well.