Heater core is leaking! E body with air !!!! Help!!!!!

On my '70 440 'Cuda with air I removed the box without removing the dash. Take it out the bottom as suggested. Tight fit but it will come out.

It might not be a bad idea to take out the seat to give your self a little more room to work.

Pull the dash...

Then you can put it on the bench and work on it without imitating a contortionist...

Makes life a lot easier...

Here's what one looks like freshly cracked open after 40 years full of paint over spray, dirt, dust and leaves. Most of the insulating foam is gone on the doors.

. This is mine before I took it apart. If you left the firewall part in place then you wouldn't have to break the AC lines open...back in the day I'm thinking?

Thanks for the advice and pics. Seats and center console are coming out. Looking forward to getting this fixed

Your next problem is getting a heater core. I was going to replace mine but wound up having the old one boiled out and pressure tested as the replacement cores are not nearly as substantial as the originals. I was worried that it would metal fatigue as the mount was not as mechanically sound as it should be, IMO.
As mentioned before, get the DMT kit. It was easy to install and replaced a lot of foam powder that was all that was left from the original heater.
Craig

For just a heater core replacement, No way would I pull the dash.

as mentioned ,,,pull the pass side seat,right kick panel and the lower trim along the bottom of the dash. ( I doubt removing the console would matter match either way)

roll the ac box out from under the dash and rebuild it on the bench. I think trying to split the box while in the car is way more difficult than us old guys want to deal with .

One thing I do when I do heater cores is that after all gaskets internal and external are replaced, which you are going to do, is I get out a hand held vacuum pump and move all the doors to make sure they move freely. If not, I trim the new foam where necessary or replace the vacuum operators.

When I replaced the heater core on my Brand F ponycar I had to pull the dash. While you do not have to, you may want too consider this. I took the opportunity to tighten every bolt and nut in the dash assembly to ensure a rattle free dash.

Anyy my job was on my DD, so I had to get it done.

Another vote for leaving the dash intact. Disturbing a wiring harness and your gauge connections will risk adding to your nightmare unless you plan a full tilt refurbishing. DMTs gasket sets are great. Just make sure you take lots of pictures as out disassemble because the kit instructions only include pictures of correct gasket and seal locations and not reassembly instructions. Get a FSM so you can calibrate the external linkage correctly. Pull both cowl vent hoses and vacuum out your cowl. You won't believe the crap you find. Wear a mask when you disassemble. Nasty, loose fiberglass rust and ancient dirt and leaves and crap await.
Consider flushing your AC core while it's out. Pour in a quart of mineral spirits. Let soak, slush it about. Blow it out with compressed air. Follow up with a quart of lacquer thinner and do the same. Blow it out real good and leave it out so all will completely evaporate before reassembly.

Here's a little food for thought. I had to do the same job on my 68 B body w/ AC. I could not find a replacement heater core anywhere. Everyone carried the non-AC heater core, but nobody had the AC version. I ended up getting a custom one supplied by one of the aftermarket AC shops (I believe it was classic auto air). Cost over $400. Now I didn't pull the dash but was still a pain to change the core. When all was said and done, I realized I just don't really drive the car enough to need heat (although I do live in CA).

Just sayin, definitely think about how much you use the climate controls before going through all the effort. I personally feel the money woulda been better spent on the AC, since I typically take the muscle car out on nice days.

Also, if you DO want heat and AC you should consider yanking your whole box and putting in like a classic auto air or vintage auto air replacement box. Then EVERYTHING is new and works awesome. No nickel and diming replacing this and that 40 year old broken part. And the new climate boxes can be purchased servo controlled so no more vacuum leaks.