I need to know what Line output converter exactly i need to use to replace my head unit in a 1994 Maxima SE.

 

if you're only replacing the head unit, you need one that will change the speaker outputs on your HU to linelevel outputs for the OE speakers.
But I'd suggest just swapping in new speakers, as the OE ones are pretty crappy after 10 years.

 

What he said!!! The Bose adapter will cost as much as one of the pairs of speakers you will need.