the thing is, i didnt have a plug going into the factory radio. the wires just went straight into it, so i had to cut them to get the radio out.
there should be a plug somewhere in the dash then, might be hidden somewhere and stuck on a bracket, but it'll be there if you just cut the wires off of the deck
if not, take a test light or multimeter and check the wires, with ignition on, you should have power to one or two of your wires, if there's power to two, then you have a constant (will be yellow on a new deck) and a switched (red on new deck), turn the ignition off and check them again, the one that turned off is obviously the switched, if you only have a switched power wire, you need to run one to the battery
the one with the plug is the antenna
the rest will be a ground and the speaker wires
to find the ground, repeat the test above with a known power wire, and touch the others one at a time to find the ground using a test light or multimeter
after you know the ground, put power to one of the remaining wires, then touch them one at a time to a ground, when you hear a noise from a speaker, those two are a speaker pair
but as I said, you should have the factory plug somewhere in your dash still, just follow the radio wires to it
