[Arran]

So the Radio Shack deck doesn't have a line level output for the 8 track player? I have a quad eight track/tuner/amplifier in storage, but it's a cheapish unit, it probably uses op amps or TO package transistors for the output. Do you need the quadraphonic function or just the standard stereo output? My inclination would be just to pick up a stand alone component style 8 track player, with a line level output, it's not like they are hard to find. To modify the Radio Shack unit is something you would need a schematic to do.
Regards
Arran