You can buy the mass air conversion kits from vendors but you'll need a used automatic(not manual) donor ECM/computer from a 1989-93 Ford vehicle long with the mass air sensor and air intake parts. One from a Mustang or possibly a Mark VII would be suitable.
How To Install Fox Body Mustang Mass Air Conversion (86-88) (lmr.com)
1986-1993 Fox Body Mustang Mass Air Meter & Conversions (lmr.com)
How To Install Fox Body Mustang Mass Air Conversion (86-88) (lmr.com)
1986-1993 Fox Body Mustang Mass Air Meter & Conversions (lmr.com)