Need help with radio

[levus]

I just bought a 1993 land cruiser FJ80 and the radio had been stolen out of it. Im not sure if it had a factory radio or not, but there are some wires hanging out that appear to be aftermarket speaker wire (the typical silver and copper wire incased in clear rubber) and there are 5 pairs of those hanging out and a power wire and a ground but the ground is very weak and there is no power to the red wire. But, behind that there is a box labeled "fm modulator" and three plugs that are not plugged into anything and when using a test light, i see that there is power to at least one of the plugs. Were those the original radio plugs? If so, why did they wire up aftermarket speaker wire? And how will I hook up my new radio? Will I need to buy an adapter to hook into those open plugs? any advice would be appreciated. thanks