Special marriage act

Sir,

I am a christian and I m willing to marry my fiancee who is a muslim. Her family is ready for a marriage under Special Marriage Act however, they have insisted for a nikkah ceremony before that. For performing nikkah I have to convert to islam. After nikkah ceremony whether I can do a register marriage under Special Marriage Act?

Your reply in this regard will be highly appreciated

Regards

Ajay Mathew