None of them. The best of turds will be the front speakers.
The radio outputs a MOST signal for use by audio amplifiers
. I don’t believe anyone made one for a Gen 1.
You can get a DAC like this
Today's modern vehicle audio systems are becoming increasingly more sophisticated and complex. PAC engineered AmpPRO to dramatically simplify the installation of upgraded amplifiers in data-bus-controlled amplified sound systems.
catalog.pac-audio.com
And that’s a true untampered digital signal. Again though… Nothing like that for Gen 1 that I’m aware of.