AK, you drive truck too? All you need is one valve on the supply line to the heater core.
Damn Freightshaker that I drove you had to open the valve for heat and then regulate how much heat you had in the cab buy rolling the passenger window up or down.
In the summer you just closed the valve and the A/C worked great.

 

hi folks,

just to let you know it was leeking heater core and the whole dash had to come of and the core replaced. Quite expensive but what can you do if you don't have proper garage.

Thanks for all your help.

Best regards
Frank