Found a small sub that fits inside the center console.
It sounds great for it's size!
It get its feed from the speaker outputs on the original Delco radio.

 

That's pretty nifty. What kind of wattage are you running to it?

 

The sub is active, so it has a built-in amplifier of 150 watt peak.
Power is connected to one of the two power outlets underneath the radio. Works great. Gets the amps it needs.
I also made an aux input on the old Delco radio/cdplayer, and swapped all six of the original speakers for some nice new JBL GTO's, so the stereo system is pretty good now, and it looks 100% original

 

Subs & Component Speakers ? KSC-SW01 Features ? Kenwood UK