Buddy of mine is running a 3 core radiator (from ebay) in his MK3 and fitment was fine. The problem he had was the poor packaging for shipment. The radiators are simply boxed in a single walled cardboard box. There's not protective cap placed on the inlets and outlets so they easily eat through the box during transit and get damaged when exposed. The first rad had to be returned because both nipples were crushed beyond repair. The replacement was delivered the same damaged but we were able to straighten the nipples enough to use it.