How Much Horse Power do I need to Pull the front end off the ground ? 
The first thing to understand is the amount of HP your motor puts out is only a small part of pulling Wheelies, Yes if you have 500hp your present VW would most likely pull some impressive wheelies with Brute HP alone. 
  We once had a stock 1200cc 40hp Pan Buggy in the shop that was all most impossible to start out with out pulling a wheelie. Very short wheel base helps a lot.
Suspension can also make a big difference. Set the front up with lots of travel and very soft so the front end sits low. Now when the clutch is let out it takes very little HP to start the front end moving  upward, and once moving in the upward direction it takes less HP to keep it traveling in that direction.
Now set the rear end up with lots of travel and as soft as you can, but still keeping it at the top of it's travel. Now with the Rear suspension setting High and soft as soon as the clutch is let out, the rear end drops and the front end starts up and the wheelie is starting even before the front end leaves the ground. Now we need just a little help to keep it moving up.
Not as important as Wheel base Length and Suspension is the front end weight, amount of traction and horse power. If you don't have the traction the HP is not very important.
 If I have missed something important e-mail me and will do the corrections. Have a nice day and remember a good wheelie car is also normally an evil handling street car.