Hy Rambos Ride, yes that should be a single system master, [rectangular cap], as to the booster, that is usually mounted after the master cylinder on that vintage of truck. They're called remote boosters, Hydrovac is one name for them. I personally would not bother to install a dual master cylinder, a properly setup single system will work [and have] for many years, hope that helps.
Thanks - are the master cylinders available rebuilt or at least a kit? Too late to call NAPA tonight!
