[nuugen]

I have found someone who makes an adaptor plate to go from the W12 to an Audi manual gearbox - he makes the kit for the C5 RS6 and that shares the same bolt pattern as the W12... but... the kit is over $2,000 which I don't have.

Is the guy here in the states by chance? I know of someone that does the conversions for RS6, A6 4.2, A8/S8, etc.
BTW, I love that you are tackling this type of project with THIS powerplant. There are dozens of alternatives and ppl are always going to ask "why use this engine when you could use that one," etc...I like seeing a project that goes outside the lines of what a "normal" swap would be. I heard the same rhetoric way back in 1995 when I decided to build the world's first Scirocco VR6..MikkiJayne could understand I know!
Keep on trucking mate, I will be watching this post.