more 4KQ questions

[dieckeaw@PLU.edu]

2 of my friends and myself are dreaming of the day we all own 4kq's.  
We've been talking about performance mods, lighting mods, etc.  We're 
curious, they come with 195/60-14's stock, right?  If we were to put 15" 
wheels on the car, what size tire do we need to go to to keep the same 
overall diameter?  Also, what's underneath the rear seat on the 
quattros?  Is it empty, or is it filled up with rear diff and other 
mechanicals?

One more thing.  I posted a question about Mercedes's involvement with 
Audi in the late 60's and early 70's.  We had a '73 100ls and I was told 
at that the car was modeled after a Merc model, and it even had a Merc 
engine in it.  Is this true?

-Adam