egad, two ways to displacement increase - bigger bore (ln nickies) or longer stroke (different crank).
info on bore here (check bottom of page):
"Nickies™" for the Porsche Boxster, Cayman, and 911 Models
and info on stroke here:
AUTOFARM | Performance Options
the ln info sets the limit on bore increase, but I've read in jake's past posts that he can go bigger with some specific castings. so, methinks to get 4.0 out of a 3.2 you are pushing the bore to the limit on specific engines only and sticking a crank from a later m96 or m97 in (which requires much revision to carriers, bearing surfaces, etc.). and then you have to deal with a 4.0 trying to breathe through 3.2 heads which means either a lot of machining or later heads.
it's like the ax analogy - "I've had the same ax for 20 years, changed the handle a few times and the head a few times, but same old ax" - probably not much left of the original 3.2 once done.