With either engine the stock heads are going to kill the power.
You might as well just go 82x94 and dual 44 IDFs. Get Steve Tims at
www.performanceworkshop.com to build you a set of heads. The price of his heads includes porting your intakes, setting valve spring pressure for your cam, head ccs about perfect for a 2.0 liter stroker with .040-.060 deck and modifying port volume if needed. That is service you just can't get out of an off the self head and his heads are cheaper than compareable CB heads. Tuned properly this combo with a W 120 cam this combo is about 160-180 hp with a very wide power band from 2000-6000. Sticking with the VZ 15 cam will make the torque come on even sooner. I have used both cams. The 2109 engine you list will also pull real hard with the VZ 15 cam and a set of Tims heads. The Kads will work fine but dual IDFs will make more power. Here is a link to a dyno chart of just how wide the torque power band is with a 2275 and W 120. The VZ 15 should come on a good 500 rpms sooner which is very helpful off road.
http://images.thesamba.com/vw/gallery/pix/396094.jpg