I removed the one in my 58 and replaced with a valve similar to this one.

https://www.ebay.com/itm/HVAC-Heater-Control-Valve-Heater-Valve-Vacuum-UAC-HV-5952C-/222504090873

It has 4 hose fittings on it, with no vacuum, it flows water through the heater core, add vacuum, and it bypasses the heater core. Sorry, I am not at home and don't have the part # that I used with me. I can post it when I get back home but, it will be a week.

I leave it on during the winter and then put vacuum to it to bypass in the summer. I have not done anything to control it from in the cab though, I have to get out and lift the hood.

Mike
1955 Chevy 6400 ex-flatbed (no bed now!) sold September 2023
In the Stovebolt Gallery
1958 Chevy 6400 flatbed W/dump
In the Stovebolt Gallery
1959 Chevy Suburban Owned for almost 20 years, Daily Driver -- sold May 2016
In the Stovebolt Gallery

Sufficient unto the day is the evil thereof