57-59 deluxe heater control valve

[2Jhead]

Hi guys,

Anyone know where to get said valve? Mine's leaking. The 55-56 one with 5/8" tubes is all over the web but I can't find the later one which I want. The parts houses say that the older style will fit well on 57-59 but I can't see how it would when the tubing is the wrong size. Specifically the 90deg elbow would need to step up from 5/8" to 3/4", don't know where to get such a part. Any tip on how to move forward is welcomed!