HUF Deed for an already existing HUF

Hi,

My father has an HUF (account and PAN), which was opened long time ago when a legal deed was not required. Now, we are planning to add some assets on to the HUF and a legal deed is required. What should be the format of this deed? same as the HUF creation deed?

Also, my mother passed away a few years ago, and there are only 3 family members left(Father, me and brother). Does this impact the deed in any way?

Thanks