If the vehicle is your only mode of transportation then you should be able to insure it
since you have an "insurable interest" in the vehicle. However, if you are involved in an accident where you are considered at fault then your father's estate could be held liable for the damage you caused. Getting the title transferred to your name as quickly as possible should be your most pressing concern, but you should be able to insure it while you're waiting so you are able to legally drive the car. If you are the executor of your father's estate then you may actually be able to add your name to his policy if it is still in-force until the policy renewal. I would recommend contacting the company that insures his car currently for assistance.