Rainierman

I have 1993 Suburban K2500 and it just died on me. I brought it home and ran the OBD1 diagnostics. I came up with a 75, 85 and 86 code. On the 75 code I don't thnk the EGR would keep it from running. On the 85 code it says the PROM may be bad and the 86 code says the EMU may be bad. I have power to the pink wire at the coil, but thats as far as I have gotten. I don't want to replace the ECU and Prom unecessarily. What should I be checking? Any suggestions would be helpful. It's a 7.4 L TBI engine and I think a 4L80E trans.