The TPI system has a lot of wires going in all directions,
which looks pretty intimidating, but if you.
break it down to the facts, it's not impossible to wire in.
Here are a few pictures and sketches made to make a TPI engine swap easier
for others to do.
Lots of answers were found in the 1987 Firebird Shop Manual.

 

These are the EFI harness to vehicle harness junction connectors, and they are to be connected to the existing electrical system in the Chieftain. This really looks much worse than it is, as most of these wires in fact connect to each other, and a few will be left out.

The VSS buffer, also seen in the above pic is connected like this: -The Vehicle Speed Sensor (VSS) is connected to the first two wires. -The purple and black wire to ignition (+) -The brown one to the Engine Control Module (ECM). -The Cruise Control and Speedometer wires can be omitted in an old car -The black and white wire goes to ground.

Here are the two large connectors and the ALDL (diagnistics) connector also seen in the first pic above. This leaves about eight wires to be connected to the vehicle, one of which to the ECM wire on the VSS speed buffer above. -C Service Engine Soon (SES) light -D Fuel pump feed -F & G + Hot in run (ignition on) -K to VSS Buffer -M to Ground -N to Neutral switch (grounded in Park or Neutral) -P Torque Converter Clutch control (+ in run, but not when brakes are applied). -R +Hot in start only

 

The EFI harness, seen here lying on the floor has had all connectors marked to aid mounting to the engine in the 1957 Pontiac. This harness also connects to the + terminals on the battery and the alternator.

At this time most of the electrical system is mounted and the EFI harness is connected to the old electrical sytem in the car. The Engine Control Module (ECM) connectors will connect to the (surprise!) ECM, which will be tucked up under the dash. (March 2011)