Gonna be a big job to swap from and injected car to a carb. I did it, and it was a big job, except I stayed injected. Same year to same year, and it's something I'm not too sure I'll do anytime again soon. And honestly, the 79 5.0 is all but the same undercarriagewise as you 89. The hardest part is gonna be getting all the wiring and fuel stuff squared away. I say go injected, but that's just me.