Missed these questions you posted earlier.
We know the atlas Howard used. However, I'm not sure if we know what kind of projection was exactly used. No one who owns the map book has provided such information. Given the time frame there are only a few possibilities. I used a map program to superimpose Howard's map on a globe. I used either a Polyconic projection or one other that I can't remember now and using many control points. It worked pretty well.First, what type of projections were used in the maps of Europe that Howard traced? Is there any information on the actual atlases he used? If we match the projection, we will know how his map should lie on the globe. If we match the atlas, we will see first hand the details that may have influenced his choices.
The original Howard sketches exist still today. There are three of them. They may be all that ever was or there were more but in that case they have been lost.Second, the original Howard maps: Do any originals still exist? If so, have they been scanned or photographed with modern technology? As a final touch, it may be possible to capture grain, smudges, wrinkles, and other such minute details, and use those to add an extra layer of "original" randomness to the seed for height-map terrain generation.
You should check the largest map thread on conan.com forums. There are high quality scans of the Howard's sketches and the name of the book is also found there. I would start looking from the latest posts rather than the earliest.
Howard really gives no explanation of this situation. So people have theorized many things. such as Conan renamed the city, Conan movied his capital or that the words have slightly different meaning. E.g. Tamar woud mean the 'old city' part on the hill and Tarantia would mean the larger city around it. The latter two options have precedents in the stories. I on my map ended making them two different cities. Partly because I wanted more cities on the map, the geographic clues given in the stories allowed this option and there was nothing that directly contradicted this in the stories.I've read that Conan moved the capital (as opposed to renaming it), but that may just have been someone's hypothesis. But at least we have a fixed location for Tarantia, according to REH's map.