Is the heater core inside the cabin behind the glove box? Might try taking off the top of the dash and see if there are any brackets there. If all items are outside under the hood might look near the base of the windshield and see is there are any screws there. Might have to remove the windsheild wiper and possible the trim strip at the bottom of the windshield also. If you have a Haynes repair manual # 24045, I found this information on page 3-8.