Keeping the stock setup for awhile, not sure of I can get away with 4 ohm speakers, I know some fords used 6 ohm.
I would like to know impedance of door speekers. I don't have them, but the wiring is there.
Nobody knows?
It will be 4 or 6. You'll be fine even at 4 ohms; DCR and impedance rise will keep it in line.