No, no they're not.

They're both 12V injectors. The resistor box limits the injector current because the injector coil is a low impedance (low resistance) type. The OBD1 injector coils are high impedance and effectively current limit themselves (because the coil impedance is high enough).

I could see how you'd get confused and think they were 5.5V or whatever if you measured voltage between the injector and resistor box while the injectors were firing. There would be a voltage drop across the resistor box when the injectors are firing, and the almost-squarewave signal might average out to be 5.5V at a certain RPM if you're using a multimeter. But no, they're not 5.5 V injectors. When the injectors aren't firing, you'd measure 12V at the same spot (no current means no voltage drop across the resistor box), and if the RPM changed you'd see some other value than 5.5V. Your multimeter is playing tricks on you because you can't actually see what that signal looks like with a multimeter.

Just to repeat what I already said, you can either use the low impedance injectors and a resistor box, or the high impedance injectors without a resistor box.