I'm so sorry to read about the loss of your Dad, and your right of course 67 is not a big age these days, having said that my wife was only 66yrs. The fact your Dad appeared healthy too leaves one asking questions, but of course we can go at any age, having lost your Mum and now your Dad you will find it tough, your grief will feel unbearable at times, and you will keep asking yourself.. WHY.. and can how life can be so cruel.
I'm 71, and if it's any consolation, which I doubt it is right now, going peacefully in my sleep is how I'd like to go...as indeed most of us would I'd imagine when it's our time. I lost my Dad who was my best mate some years ago, and I still miss him, and indeed still shed tears...mainly when I play back old family camcorder recordings. I lost my wife after nearly 49yrs of marriage in April, so I'm grieving very much for her right now, there is nothing worse than losing a close loved one....but you are not alone, you are among friends on here.
I wish there were some words I could share with you to lift the pain your are feeling right now, sadly there are none, other than to assure you, all of us here have lost a close loved one, and we understand, and know how you feel, grief affects each of us differently, some recover quickly, while for others it can go on for years, and I'm sure for some we never stop grieving. All you can do is to take it one day at a time...posting here is a start as sometimes it helps to let it out...
You take care of yourself....