If i were to get a complete donor car like an 01-02 z28/trans am and i swap the drivetrain as well as the dash components and the fuel system would i still need to get a wire harness from painless or any other place?

 

Not from painless, but there are some connections that would have to be made. Depending on your level of electrical expertise, you might be able to do it yourself. Otherwise, you might consider sending key harnesses to someone like 'Pocket' on these boards.

 

other connections like what?

 

The engine harness on a thirdgen has two main connection points:

The C100 (big black connector by the brake booster)
C230 (small black/clear connector under the dash passenger side)

C100 has the wiring for the main power into the car, alternator power, ignition power to coil, oil pressure and temp gauges, starter, etc

C230 has the wires going to the aldl port, speedometer, injector power, etc

As well as the harness having the relay and wiring for the fans as part of the engine harness.

LT1/LS1's use two small connectors along the strut tower, and two small connectors inside under the dash, for all of their connections, as well as the fan wiring and relay locations being part of the chassis side of the harness.

Everything to the LT1/LS1 harness has to be re-routed, to connect to the thirdgen appropriate location, as well as all of the fan wiring and fuel pump wiring be added or brought over from the original harness.