I would recommend NetSim. Information on NetSim VANET is available at https://tetcos.com/vanets.html. There are examples involving clustering by interfacing with MATLAB in https://tetcos.com/file-exchange.html

Few years ago, I used the NCTU-NS simulator and emulator that was awesome in providing the control on handovers with several useful options. However, this is not free and little expensive.

To implement clustering mechanisms Ns2 or Ns3 is better.

You can look at NetSim https://tetcos.com/vanets.html

I would suggest SUMO + NETSIM

You can see this paper - https://www.mdpi.com/1424-8220/19/9/2191