Thanks so far, guys!
@BadAndy: Well, a blower would be really nice, but my car has a historic registration here in Germany, so unfotunately, the engine bay has to look quite stock.
So the way to go is build a little nasty stealth engine, put on the original 69 valve covers and paint everything blue... so nobody becomes suspicious.

@Gravel: great link! just bookmarked.
I think combining this setup with the additional cubes of a 392 stroker kit should make even more torque at lower rpm, what do you think?