It may be a Type I bottom end, but I'm not positive. Far less cumbersome VW OHC set-ups utilize Japanese motorcycle heads (which happen to share the exact same stud pattern).
The dual plug idea is something I played around with about 20 years ago ..... Type I, Type IV, 912, etc.
http://www.thesamba.com/vw/forum/album_page.php?pic_id=232010 It was a lot of fun.
Bob Denson (Kiwi) made an OHV 4-valve engine from scratch in about '84.... I wish I had a photo of a completed engine, but here's one partially assembled:
http://www.thesamba.com/vw/forum/album_page.php?pic_id=299210