PART NO.  SPL.PAGE  DESCRIPTION                                                           
AHH5422   15.R.42   Heater kit (optional), heating and ventilating equipment, 1500)
AHH5422   16.R.45   Heater kit (optional), heating and ventilating equipment, 1600 and
    1600-MK-II, and the "Duluxe" cars)

AHH5422 Heater kit complete with fittings for MGA 1500, 1600, 1600-MK-II and the "Deluxe" cars (not Twin Cam)

More information at
HR1 - Heater Tech
AHH5532 - Fresh Air Ventilation System for pushrod cars
8G9037 - Heater kit for Twin Cam
8G9038 - Fresh Air Ventilation System for Twin Cam