A custom HTML module would be perfect to add code into specific content pages. But the js code is a kind of basic advertising code (e.g. Google Adsense, but also others) that has to be added in HEAD TAG. As far as I know that is not possible with Custom HTML module, right?
There are some kind of joomla plugins, which add code in HEAD, but in all pages. So, there must be a way to use a copy of T4 / blockk template and add the code only there, but how?