In a '76 ('75-'78) the Transistor Ignition Module is above and forward of the fuse box.
The GM HEI "upgrade" that people do on the early models would work, but the wiring is a bit complex. You also have the dual pickup distributor which ads a bit more trouble ... as well as a "Top Gear" vacuum controller for the dist vacuum advance. So if you had the money to spend and not much time, then it would be way easier to buy a stock replacement (used of course). If on the otherhand you have more time and less money then the HEI module might be the way to go. But if you've got time then go out in a junkyard and find a ZX dist with integrated transistor and make the wiring even more simple.