Point website URL to subdirectory containing Drupal site

We have a dedicated IP Bluehost hosting account. The account hosts two websites, SiteA and SiteB. Each site is in a subdirectory, public_html\SiteA and public_html_\SiteB. We currently use EasyDNS to do "stealth" redirection of URLs to the subsites. For example, [login to view URL] redirects to [login to view URL] and [login to view URL] redirects to [login to view URL] The task is to have the Bluehost hosting account answer to [login to view URL] and we will remove the "stealth" redirect and simply have the A record for [login to view URL] resolve to the dedicated IP of the hosting account. We want to maintain the ability to create a new website at a subfolder (for development purposes) and preserve the ability to flip over from the production site to the development site or any other subfolder. We'll want a document explaining how to change the default directory being served, both for the web server and for Drupal. (I assume this involves editing .htaccess, etc) The freelancer should take care of the web work; I'll take care of the DNS work (changing the stealth redirect, A records, etc). The timing needs to be coordinated, so ideally the task will be accomplished by copying and editing files and providing instruction so I can backup the production files, rename the edited files, and all changes should just work. For someone that knows what they are doing, this should be relatively easy; I don't know what I'm doing.