His address should be on the front of the title, just use it, even if he had moved. That should be the one on record at the BMV. Then just date it prior to his passing. He obviously signed it prior, anyway; just left the date blank. The only thing is that you'll have to pay a little extra (at least you do in Indiana) since it will have been over 30 days or whatever your state's requirement is for getting a transfer.