Really depends on how deep you want to rebuild it. Generally a headset and pan set will contain most gaskets/seals. But then you need all of the little pesky parts such as balance shaft o-rings, plugs, etc....A rebuild is not one of those things that you can plan exactly right. More like set aside a week or 2, make room in your work area, and go through your motor to see what needs replacing and what does not. and dig into it. Take your time and things will come out right. Have a good manual that breaks everything down to the nitty gritty would be a good start. Heck, I still have the OLD Euroselect Porsche parts book for water cooled Porsches
which breaks down the parts pretty good.
I have known some that have rebuilt the 44 motor while the block was IN the car. Just removed the heads and the oil pan. Not the way to do it IMO. Takes too much time. Seen others just install a head set and called it a rebuilt motor.
Lee