1968 plymouth valiant 100 a/c vacuum diagram (factory installed) with 225 slant 6

Glad to help out. I mention the heater water valve because the pre-'71 type has been unavailable for years, or very expensive when you can find one, so often the earlier cars have been repaired somewhen along the line with a later-type (single vacuum hose) valve -- this, by the way, is a repair I'm completely onside with. Anyhow, if you find a single-hose valve, you'll have to deviate from the factory vacuum diagram to get everything working right.