My blower motor is only running on high after jumping it

Need advice I have temporarily jumped wires so I have high setting on heat or off but I need help getting this part 1985 mustang fox body lx 5.0 302 I just replaced heater core the blower resistor got destroyed by radiator fluid and I cannot find the right one anywhere I have 2 plugs for mine the ones that parts stores have listed only have the one plug what can I do I'm missing the 2 wire plug that goes to the fan engine on all the ones I can find anywhere need the second plug or if I can re wire it I need to know the right way thank you very much