You'll have to cut the top off and leave the support bars in place.
Go look at Vanagon Westy ceiling and then go to the junk yard and look at
a regular van ceiling.  I had my westy upper bed out just last week (and cabinets)
and there are a lot of holes and brackets to do in a make over.

Good luck   Malcolm S

I recently sold my 69 van, Wesphalia, but loved the interior layout, particularly the fold down bed.  I
am about to buy a 72 factory sunroof van that does not have the Westy interior. Can anyone tell me
how difficult it would be to get ahold of and install a Westy fold down bed like my old 69?  How best
should I proceed??   Thanx... Tom (Long Beach, CA)