If I buy an O E M heated power leather seat package for my extended cab Cheynne are all the wires under the floor covering or do I have to run a harness. Does the factory put the wires in and if the model doesnt require the wires do they ignore them? Thanks for any and all help

I haven't seen that option yet at the bone yard, but having removed many GM options from early 60's to 90's GM cars and trucks, my guess would be that it has it's own harness plugged into the power supply block on the firewall probably above and to the left of the brake pedal.