Careful.
Make sure they seller guarantees they will fit. I think there's a potential clearance problem from what I see.
I bought some Hella units. The rear of my Hella H1 (HI) looks a lot like the 5006's on The Auto Mall.
It won't fit in my 77. The extension is too deep and the diameter of the extension won't go into the opening. The depth of the light housing is about 2 1/8". The hole behind the housing is 1 3/4". The lamp housing extension with rubber cap is > 2 1/4" in diameter and > 3" deep. It won't fit. I don' think you can't cut enough metal away to make the hole larger behind the housing. There's a support in the area.
The Hella H4's (HI/LO) were ok. They have a flat cup behind.
See the photo's of what I'm describing at my website:
http://www.sunny-california.com/photo_gallery.htm
Before the Hella's, I bought some cheap offshore lamps from a guy on ebay. The glass was so thin it broke in shipment. They would never stand up to a pebble on the highway.
Still looking for REAL European lights for my 77. They have to meet the inspection requirements in Spain.