[QUESTION] Use marlin in EFF but ALSO have a Heated Bed

Hi, i use marlin on ramps 1.4.
my question is: Is there a way to use marlin in EFF mode but still have heated bed via an external MOSFET ?
My goal is to use both D8 and D9 pins for Fans (D10 for Heater) and connect a heated bed to it using an external MOSFET (Don’t wanna use RRD fan extender)
If So what codes in marlin must be edited to do that ? May i simply remap Heated Bed pin to a free pin ? Which free pin is suitable for Heat Bed ?