I've done this recently to my '73 NYB. It was far more easy than i thougt (A/C car). Be aware, that the heater box is made from Asbest! I used a mask while working on it.
- I removed the glove compartmend and the heating lines from the box to the vents.
From under the dash and this opening i could loose all srews that hold the inner part of the heater box.
- Then i removed the heater box by pulling it down into the footwell carefully. After that i could take out my leaking heater core (and let the AC Core in place).
- I put the brand new heater core in (fitted 99% perfectly) with new sealings from Detroit Muscle Tech. (Thanks to
@CBODY67;
@ayilar and/or
@Boydsdodge for the recommendation!).
- Put also new sealings on the heater box itself.
- Put everything in place again an reconnected the hoses. Works!
Here is my post with pictures of the sealings
Hello from germany / 440 New Yorker
Here one of the old and new heater core:
Hello from germany / 440 New Yorker
Greetings Manuel