Vr6 is probably the most logical way to swap a engine in there . If you go with anything else it's going to be very pricey since they have to use the sub frame of a leter model . You still can do many bolt ons with the 8V as well ... just you wont be going as fast as you prolly would like
here are some sites for you
www.neuspeed.com
www.adbracing.com
www.jwelty.com ( kind of a message board as well like vw vortex )
www.parts4vws.com
www.newdimensions.com