Change NT Workgroup enviro to NT Domain

I have an NT4 SP6 enviroment that is working in as a workgroup and not a domain. I am wanting to change this to a NT 4 domain. I have several servers that are in production so I don’t have the option to reinstall them. My plan is to take just a standard PC and install NT 4 as a PDC for the domain that I want to create. I then want to join my servers to the domain. Once the servers are synching as BDC’s I want to take down the standard PC that is the PDC and promote one of the servers to be the PDC. My only problem is in my test environment when I join my workgroup server to the domain it is still just a stand alone server and I don’t have the option to promote it to a PDC. Is there a way to do this that I am missing? I would appreciate anyhelp that is provided. Thanks in advance.