does anyone know if the wiring harness from my 3.4l v6 will work if i drop an LS1 in to my car?

if you have done an engine swap, how much did it all cost you?

 

the harness will not work, you are going from an OBD I car to an OBDII motor

 

Those 2 engines share no parts.
Other stuff you have to change trans, trans clutch lines, engine mounts, struts springs, trans mounts fuel lines, radiator, exhaust.
There is no way a V6 harnes is going to run a V8.
It will cost a lot a few thousand.
You could check out what I got for my v6 for about $1400, should kill plenty of V8s.