I am sorry, I misread your question. I understand the dilemma now.
You have a Hyper-V host in workgroup, which you want to manage through VMM (which is on domain) and then you need P2V a few Win2003 Server (also in workgroup) to this Hyper-V host. I have good new and not-so good news.
You can add the (Workgroup) hyper-V host to SCVMM as a perimeter host
http://technet.microsoft.com/en-us/library/cc917968.aspxBut perimeter host cannot be used as target during the p2V operation i.e. you cannot P2Ved VMs on it.
http://social.technet.microsoft.com/Forums/en/virtualmachingmgrsetup/thread/6d2398ae-07ff-4323-9cf8-561fad326440Regards,
Shahid