[Flamesuit on]
I've been looking at hi-tech options and the 4.2 Audi RS4 motor will just about fit in a 67 engine bay with the stock strut towers. It would look tiny in yours. Quicktime even make a bellhousing for it.
335Kw stock trim NA!!!!!
It's the same spec as the V8 R8 motor. There is a burnt out RS4 on the bay right now and the engine bay looks intact.