There's only 3 VK56's on car-part.com, ranging from $3,000 to 3,800. I've been wanting one bad to TT, but don't have that kind of cash right now, so a vh45 will have to do for the meantime.
They weigh 228kg's (511), all aluminum, and nothing bolts right up. You could have an adapter plate or a bellhousing made up to fit any tranny as Cookson said, if you wanted it bad enough.