I recently had the please to talk with someone about Death Heart, the module and its map. Specifically they were curious about where it fit on the Arduin Country map empcho produces.
I had good and bad news for them. The bad news is it doesn't. The good news was its still in the world just a bit farther west of Arduin these days, on the border of the nation of Talafar and Marmachand. Big names for those with any inkling of Arduin's history.
Since an explanation seemed in order, I passed on that the maps in the modules and the maps that empcho uses are not one and the same. In fact, David Hargrave redid complete country and continent maps for each of his Arduin campaigns (I - III). The "official" one is the last one he did prior to his death, which is the one empcho had digitally recreated in late '99 and sells.
Talking about Death Heart, you can find to landmarks to orient the map provided in the module. It won't be exact since the landscape has changed, but it will make sense. The Mountains of Madness are your first one of note. It lies along the border of Talafar and Marmachand and use it you can adjust the map accordingly to make sense (maps of these areas are found in the World Book of Khaas).
Considering the length of time between publishing the modules and the empcho map it should come to no surprise that they differ. Still, not all its lost. The Citadel of Thunder is on the Arduin Country Map, as is the Howling Tower. Caliban can be where ever you want it to be, which is a fun function of that module.
So, enjoy them, either in Arduin or your own worlds.