as for the roof cut there are severals things to mention:

- before you do anything take a lot of measurements of all openings (windshield, doors, ...)
- mark several reference points on both roofs (old and new) for future measurments.
- open all necessary welding points
- A and B pillar are 3-layer type - I cut a 10cm cover from the outside layer to get access to the middle layer.
- cut 2nd and 3rd layer withing the 10cm cover range but cut them in different positions - this gives you
  afterwards more chassis stiffness.
- after welding 2nd and 3rd layer weld the cover in place again.
- C-pillar: the easiest cut - only 2 layer, cut outside layer about 10cm from the top and open all welding points
- check out my webpage for some images.  

- All the work took me 2 days - all measurements are OK, doors close like new, no chassis weakness ...

Beware:
DO NOT cut pillars straight and weld them again (you can't weld the middle layer) and you'll loose body stiffness...


rgds

Horst