Yeah, the 787 is a different animal altogether from the 87. The piezo driver circuit is probably similar though, as I recall it's driven from some paralleled CMOS inverters. That 4069 inverter package is connected directly across the battery for max power to the piezo.
I just got in from a long drive, but when I get a minute I'll take a look at the one here and see if I can deduce the path, which probably includes one or more BJTs if the 87 is any indication.