Well, Ismalley just Pmed me with how he replaced heater core without removing box...Can anyone add to his procedure ...

take off the metal clips from around the heater box and then take off the bolts from both ends of the long bar that runs across the front dash and take off the nut that is on the middle of the bar.....should be like a small vertical support bar. pry the long bar away from the bolts....you will not get it off completely, but you should get about an inch to an inch and a half more of clearance. take off the metal clips around heater box and pry it open. you will only get the top part open, mostly on the driver side, from there you can get the heater core out.