wiring question

[thirstycanadian]

Here's an old-school question for you all.  I am replacing my stock AM radio (1985 Sierra K35) with the oldest Alpine tape deck ever.  The Alpine is brilliantly labeled, but I cannot trace the stock wires back far enough to identify them.  Two go to the speaker (a grey and a tan)  which is positive and which negative?  Aside from the antenna there are three more wires (black, grey and yellow) which i assume are a 12V, a ground and one to the ignition.  Is that correct, and if so which is which?

Any help would be great. Thanks.

[VileZambonie]

Best bet is either find a schematic or just use a meter.

[toplessblazer]

Black is ground
Yellow is ignition
Grey is illumination that turns on with the parking lights
The original AM radio did not require a constant 12v supply. You can splice into the cig lighter wire (usually orange) for a constant.