[nUcLeArEnVoY]

I'm reassembling my heater box right now as well due to an original heater core leak, I went with Ames' copper/brass repro and it seems to be a quality unit and held vacuum when I tested it.

Chicago Muscle Car parts does have the seal kit in stock, I bought it myself and it looks good. Only thing is, there is not adhesive on the seals so you need to apply spray adhesive. Not really necessary for the heater core pipe seals since they fit snugly around the pipes, but the square gasket definitely needs spray seal. Just bear in mind that Chicago Muscle Car parts doesn't do online orders, you need to call them. They ship pretty fast.

As expected, my orange vacuum tube going to the heater side nipple of the push/pull actuator was crumbled to nothing; and the actuator itself was so rusted on the inner nipple that same orange line was hooked to that it was beyond serviceability. Had to replace that, too.

The mounting stud that is clipped onto the corner of the heater box with the integrated ground strap was also bent beyond serviceability on mine, luckily they sell repros of it on eBay, but without the ground strap, so I got a generic groundstrap of appropriate size from Falconer Electronics. I had to relocate the large eye that used to be part of the mounting stud to the lower mounting screw instead (the one you unscrew from inside the car). The ground strap is very important.

Also make sure to replace the foam layering on the defrost diverter door. From the factory, the foam layer is stapled on (thus the staples you see). I had to pry off the staples and install adhesive foam I got from BlendDoorUSA. It's high end stuff that isn't biodegradable like the stock stuff was. And yes, you do need to cut out the two holes in the foam to match the two round holes in the diverter door. Those two holes are the "20%" of air the windshield and/or floor vents get respectively depending on the settings that the service manual is talking about.

While you're at it, you may want to replace the heater hose nipple at the rear of the cylinder head if you're running a Poncho motor. The later design uses a rubber restrictor rather than the bimetallic coil the older ones used to restrict coolant flow to the heater core. When I removed mine, the rubber was missing and that's probably because it had disintegrated over 45 years as it was the original nipple. Without some degree of restriction, the heater core is subject to earlier failure due to the slugs of water overstressing it during heavy throttle. Another option is to just place a .200 restrictor inline somewhere in the inlet heater hose going to the core from the back of the head. That's what they installed on the police car packages.