Are you sure? 60% is not massive.
Almost twice what is required for a Party to win a General Election.
Congrats to you man, I've been registered since I turned 18.
My mother works in a hospital and is more than aware of the difference a donor registered death can make.
It's not just your 'major organs' that are taken, your body is used to help people is so many other ways.
One adults skin can transform the lives of at least 12 burnt children (As you are dead the harvesting can be more aggressive than if you were alive, thus the quantity of bone marrow extractable is a lot higher also.
You don't think about it but each bone in your body can help someone with cancer. A deadly cancer which will kill then, but if you are registered you can provide these people with a new life. (remember there are 206 bones in an adult body)
Your tendons and cartilidge can go to fixing an arm or a leg which otehrwise would have faced amputation and prosthetics.
Your lungs can transform someone, possibly two peoples lives.
Your heart and valves can save a handful of lives.
See, it's not just "Dave needs a kidney" signing up is more than that, besides your hardly gonna be using your body after you die...