The whole bodies should be donated (for re use as much as possible, and then research) by default, or even mandatorily, since you don't need it any more after you're dead.

Sadly some people have weird fetishes over corpses and want them handled in various ritualistic ways, which I think holds back progress and quality of human life (through tissue donations). We used some cadaver tissue in a study and had to return it (what was left of it) afterwards!

Later we realized the same doesn't apply to tissue removed from living people for medical reasons, which to a startup made some things easier (and in other ways harder -- typically, healthy tissue isn't removed from living people, thank goodness!)

Good chance (part of) your medical records are already being used in some retrospective study, even while you're still alive.