Heater Core - this what I have to do?

[DeadheadNM]

Good write-up on replacing the heater core in an A/C equipped truck. I'm in the middle of replacing mine and wanted to add the following:

1) Get a new gasket to seal the heater box to the firewall - mine came out in pieces and is the reason the job isn't done as I didn't have a new one at hand
2) Of the two upper sheetmetal nuts, the screw for one closer to the driver side also secures a portion of harness so there are actually two nuts on this screw - I found this out after yanking a little while - one screw secures the harness the second, deeper secures the heater box
3) Place some plastic sheeting/garbage bag on top of the carpet and tucked up under the dash or your carpet will get wet
4) The inner fender absolutely has to be dropped to get at the outermost of the lower two sheetmetal nuts
5) As expected, the flapper in my diverter box was broken - I've got a NOS replacement on the way - if yours is original the flapper is likely bad and now is a good time to replace it
6) Even if you're careful there's a strong chance you'll crack the RH defrost vent if you try to manipulate it or it's duct - consider having a spare at hand
7) The glovebox insert has to be removed so now is a good time to add a glovebox light if so inclined
8) Chances are it's when not if you're going to have to replace the heater core and the brass/copper US made ones are no longer available to my knowledge but Mexico-made ones are (at least for now). Otherwise, you're left with aluminum - not sure country of manufacture on these.