I have often considered something like that... I think the MK4 setup would be the easiest fit since the chrysler products use a similar mounting system.. The only hiccup would be axle shafts but that might not be a huge deal if you get creative.. Both have the same 5X100 lug pattern so it might be as simple as some custom wheel bearings to use the VW hubs in the crysler knuckles. They are very similar in width but I haven't measured it exactly.. When I was measuring up things to do a Focus ZX3 swap the width of the wheel hubs was within 1/2" of the VW, and the front suspension design was the same so I was going to use the VW knuckles/brakes with the Focus lower control arm re-drilled to accept the VW ball joint.. Good stuff..
CFM, I've been following your Saturn thread from the beginning.. Very nice work.. I think the PT will be easier to fit physically partially from the chrysler using the same type of mounting system without a big subframe underneath..