From an installation POV, I don't get how fuel injection is so much harder - The harder part would be the installation of the fuel return lines - But with them already there, you're talking about the ECU sending signal-level voltage to 6 injectors - After that you're just talking about the differences in sensors and maybe 3 sensors at that (For generational purposes, O2 sensor, maybe the knock sensor, and... Maybe cam-angle as well as crank angle ?