There was a bolt-on adapter from Contemporary once which added a lot of weight and track in the front.
The rear used a similar setup as ERA's.
I can only advise to get a 6-pin set. Because you avoid a lot of trouble which we are busy solving here:
Pin drive bolts splitting Help Please
I also have a set of new 15" 6-pin wheels near Frankfurt/Germany.
The backspacing of the front MK4 are completely different than what mine have and you want.
I tried MK4 wheels on my RAM and they stuck out big time.
Dom