After I remove the amps from my aftermarket stereo how do I get it to run off the Stock head unit again?

Thanks

 

Reinstall the Stock HU, and reconnect the factory speaker wiring back to the speakers.
Although, i could just be talking out of my a$$....

 

LOL.....

Canuck.... I assume you are referring to adding aftermarket amplifiers? You will need to get a line output converter to convert the speaker level outputs from the factory deck to low level RCA type outputs that an aftermarket amplifier can use. You can also wirethe speaker leads directly into an amplifier that has high level inputs. The only decent amps that I'd use that use high level inputs are Rockford Fosgate or Xtant.

http://www.peripheral-aamp.com has some specifically designed for Nissan systems, though theya re not the only type out there. If you have a Bose system I wouldn't get any other type than the Peripheral Vendetta series converters.