69GMCLWB 396 A/C Question

[Wildbillvette]

Hello Guys,
Was going to install heater cutoff vacume valve on inner fender of my truck.
Looking in my shop manual it looks like its not supposed to have one. THere are no holes in the inner fneder but it has been replaced. looked on the heater control switch and it has a port or thee vacume hose to the valve but then again it has beeen replaced as well. There is no vacume line running from the control to where the valve would be on the inner fender. Anyone have a really original 69 396 w a/c that can tell me if there should be a heater control valve to shut off the hot water to the heater core when the A/C is turned on? I looked in my assy manual and 68's dont have the valve 72's do but I cant figure out what year it was added. I dont want to instll one if it wasn't there originally. Thanks in advance for any help.
Bill