if your not using an ECM then all you need is the wires to the starter, battery, alternator and distributor
Don't forget the wiring to the AC Fan and Compressor too, if you are using them. I am doing the same swap as you are in im 84 Grand Prix...I assume Chevy 350???. I plan to delete the ECM. I was fortunate enough to buy a dealer service manual on eBay for the 84 GP/Bonneville. The ECM wiring is in with the AC/Heating wiring (passenger side). I plan to work on that soon, maybe tonight. That needs to be seperated.
The wiring on the driver's side bulkhead is pretty much essential. There are 2 halves to this connector. One includes headlights, wipers, turn signals, etc. The other is for the egine (dist, oil send, temp send, starter, alt send, 2 red wires to power up everthing else...etc). As for a schemtaic, there are several pages in my book on this. Some of the better Chilton's or Haynes manuals have the schematics.
The easy thing would be to get a wire harness for a G-Body (Monte or GP)with a Chevy 305 (again, I am assuming you are using a Chevy 350, not an Olds 350). Easier said than done, however, as I have seen so many hacked up in the junkyards that they were not worth getting.